How to Fix App Signing Errors on iOS

How to Fix App Signing Errors on iOS: Complete Guide for 2026

App signing errors are the bane of sideloaded app users. They appear as cryptic messages like “App could not be installed,” “Invalid code signature,” “The application could not be verified,” or simply a silent failure where the app disappears from your home screen shortly after installation. Understanding what signing errors actually are, and why they happen, is the key to fixing them reliably.

Find Your Error

Start with the exact message you see. Each one points to a different cause:

Message or symptom	Most likely cause	Guide
Unable to Install: integrity could not be verified	Broken or edited IPA, revoked certificate, or device not in the profile	Integrity error fix
[App] requires iOS [version] or later	The IPA was built for a newer iOS than yours	Newer iOS required fix
Icon stuck on Waiting or Installing	The download stalled: connection, storage, a restriction or a revoked certificate	Stuck install fix
Untrusted Enterprise Developer	The developer has not been trusted in Settings yet	Untrusted Developer fix
Unable to Verify App / Not Verified	iOS cannot check the certificate with Apple: no connection, or a revoke	Unable to Verify fix
Maximum number of installed apps	The free Apple ID limit of 3 active apps	3-app limit fix
App stops opening about a week after install	A free Apple ID signature lasts 7 days	7-day expiry guide
Every app from one installer stops at once	The shared certificate was revoked	Revoked certificate guide
Signer rejects your certificate files	Wrong p12 password, expired profile, or a certificate the profile does not include	p12 and mobileprovision explained

What is App Signing and Why Does iOS Require It?

App signing is a security mechanism where every iOS app must carry a cryptographic signature from a trusted certificate authority: specifically Apple. When you install an app, iOS checks:

That the app has been signed with a valid certificate
That the certificate has not expired
That the certificate has not been revoked by Apple
That the app’s contents have not been tampered with since signing

App Store apps are signed by Apple directly. Sideloaded apps are signed with enterprise or developer certificates, which is why they require extra trust steps and are more susceptible to signing errors.

Common Signing Error Messages and What They Mean

“Unable to Install [App Name]”

This error during installation usually means:

The IPA file is corrupted
The signing certificate is invalid or has already been revoked
The app requires a higher iOS version than your device runs
There is insufficient storage space for installation

If the message adds “because its integrity could not be verified”, see our step-by-step guide to fixing the integrity error.

“App could not be verified” / “Unable to Verify App”

Appears when launching an app that iOS cannot validate against Apple’s servers. Causes include expired certificates, network issues, or untrusted developer certificates.

App Installs Then Disappears

The app icon appears briefly after installation but vanishes. This indicates the signing was rejected silently by iOS: most commonly due to a revoked certificate or an entitlement mismatch.

“This app is damaged and can’t be opened”

This wording is a Mac (Gatekeeper) message, not an iPhone one. On iPhone, an IPA whose contents no longer match its signature, because it was modified after signing or corrupted during transfer, usually fails with the “integrity could not be verified” error above.

Fix 1: Use Scarlet iOS for All App Installations

The most effective way to avoid signing errors is to use a signing tool that actively manages certificate validity. Scarlet iOS signs each IPA for you at installation time with its current shared certificate, which avoids manual signing mistakes. It cannot prevent Apple from revoking that certificate.

You can get it from our Scarlet iOS install page.

Go to scarletios.com in Safari.
Install Scarlet iOS via the Direct Install button.
Use Scarlet iOS for all future app installations instead of downloading and installing IPAs manually.

For more context on how this works, read our guide on sideloading apps on iOS 26 and iOS 27.

Fix 2: Reinstall the App with a Fresh Signature

If an existing app is throwing signing errors, reinstalling it via Scarlet iOS resolves the issue by applying a fresh, valid signature:

Delete the problematic app from your home screen.
Open Scarlet iOS, find the app, and reinstall it.
Trust the certificate in Settings > General > VPN & Device Management.

Fix 3: Verify the IPA File Integrity

If you are sideloading an IPA you obtained yourself (rather than from Scarlet’s library), a corrupted file can cause signing errors even when signing succeeds.

Re-download the IPA from a trusted source.
If the source provides an MD5 or SHA-256 checksum, verify it matches using a checksum tool before installing.
Avoid downloading IPAs from sketchy sources: they may be tampered with or contain malware that breaks signing.

Fix 4: Check iOS Version Compatibility

Some IPA files include entitlements or framework dependencies that are not available on older iOS versions, causing installation to fail with a signing-related error message.

Check the minimum iOS version required by the app (see how to fix “requires a newer version of iOS”).
Update your iOS if a newer version supports the app: Settings > General > Software Update.
Look for an older IPA version of the app that is compatible with your iOS version.

Fix 5: Fix Entitlement Issues

Advanced sideloaders who sign IPAs manually using tools like AltStore or Sideloadly may encounter entitlement errors. Common entitlements that cause problems:

com.apple.developer.networking.multipath: Requires an Apple-issued developer certificate
aps-environment: Push notification entitlement; requires paid developer account
com.apple.developer.nfc.readersession.formats: NFC access; restricted entitlement

If using AltStore or Sideloadly, the tool typically strips unsupported entitlements automatically. If signing manually, remove the problematic keys from the entitlements file you pass to your signing tool (for example codesign or ldid), then sign again.

With Scarlet iOS, signing is done for you, but an app can still lose a feature if an entitlement it needs does not carry over to the re-signed app.

Fix 6: Restart and Trust the Developer Again

iOS has no setting to clear or reset certificate trust by hand. What you can do is restart and confirm the trust step again:

Restart your iPhone.
Connect to the internet. Apple says the device has to check the developer’s certificate with Apple when you trust it, and again from time to time.
Go to Settings > General > VPN & Device Management, tap the developer under Enterprise App, and confirm it is trusted. If it shows a Verify App button, tap it.
Try installing or opening the app again. If the developer entry is gone or will not verify, the certificate has probably been revoked.

Fix 7: Check Date and Time

Certificate validation is time-sensitive. If your iPhone’s clock is significantly off, iOS may incorrectly calculate that a valid certificate has expired.

Go to Settings > General > Date & Time.
Enable Set Automatically.
Restart your device and try again.

Preventing Signing Errors in the Future

If you are not familiar with signing, install apps through Scarlet iOS rather than signing manually, so the signing step is done for you.
Keep Scarlet iOS installed, so you can reinstall apps quickly after a revocation.
Reinstall apps periodically if you notice unusual behavior that might indicate certificate issues.
Back up the data of apps you care about, since a revocation can come at any time.

Understanding Certificate Revocation

One signing error cause that cannot be “fixed” locally is certificate revocation. When Apple revokes a signing certificate, all apps signed with it stop working simultaneously: often affecting many users at once. This is a deliberate enforcement action by Apple against certificates used for mass sideloading.

Scarlet iOS does not publish how it manages its certificates. When a revocation happens, you install the newly signed Scarlet and reinstall your apps through it, and how long that takes varies. Signing apps with your own Apple ID avoids one shared certificate being revoked for everyone at once, but those apps have to be re-signed every 7 days.

For a broader look at how this ecosystem works, see our overview of how Scarlet iOS works.

Final Thoughts

Most app signing errors can be fixed on your iPhone; a revocation is the exception, because it needs a newly signed copy. The most effective prevention is using Scarlet iOS as your primary installation tool, and the most effective fix is reinstalling the affected app through Scarlet iOS to get a fresh signature. Download Scarlet iOS and put signing errors behind you.

How to Fix App Signing Errors on iOS