Fix Untrusted Developer Error on iPhone: Step by Step
You just installed an app through Scarlet iOS, tapped the icon, and got hit with a message that reads “Untrusted Enterprise Developer” (apps signed with your own Apple ID show “Untrusted Developer” instead). The app refuses to open. This is one of the most common issues people encounter after sideloading on iPhone, and the good news is it is completely fixable in under two minutes. This guide walks you through every method, from the standard trust flow to deeper fixes when the Settings option simply does not appear.
Why Does the Untrusted Developer Error Appear?
Apple requires all apps to be signed with a verified certificate before they run on iOS. Apps installed through the App Store carry Apple’s own signature and are automatically trusted. Apps you sideload through tools like Scarlet iOS are signed with a developer certificate that Apple has not personally vetted, so iOS flags them and asks you to manually declare that you trust the developer behind that certificate.
This is a security gate, not a sign that anything is wrong with the app itself. Apple introduced this mechanism with iOS 9 and it has remained in place through every release since, including iOS 27. Scarlet iOS signs with an enterprise certificate, so the trust step is a one-time action until that certificate is replaced, for example after a revocation. With tools that use your own free Apple ID (AltStore, Sideloadly), you trust your own account once; the apps still have to be refreshed every seven days.
For a broader look at certificate problems, see our guide on Scarlet iOS Certificate Revoked: How to Fix It Fast.
Step-by-Step Fix: Trust the Developer Profile
Step 1: Open the Settings App
From your iPhone home screen, open the Settings app. Do not tap the sideloaded app again: doing so will just show the error repeatedly without giving you a path to resolve it.
Step 2: Navigate to VPN and Device Management
Scroll down and tap General. From there, scroll down toward the bottom and look for one of the following options depending on your iOS version:
- iOS 15 and later: VPN & Device Management
- iOS 14: Profiles & Device Management or Device Management
- iOS 13 and earlier: Profiles & Device Management
On iOS 15 and later, VPN & Device Management is always listed. If it shows no Developer App or Enterprise App section, the app’s signing information has not registered, which points to an installation problem rather than a trust problem. Jump to the troubleshooting section below.
Step 3: Locate the Developer Certificate
Inside VPN & Device Management, you will see a section labeled Developer App or Enterprise App. Tap on the certificate name listed there. It will typically be an email address or a company name associated with the signing identity Scarlet iOS used for that installation.
Step 4: Tap “Trust”
On the certificate detail screen, tap Trust “[Certificate Name]”. A confirmation dialog will appear. Tap Trust again to confirm (on iOS 18 and later the button can read Allow & Restart). Stay online, because iOS checks the developer with Apple.
Step 5: Return to the Home Screen and Launch the App
Go back to your home screen and tap the app icon. It should now open without showing any error. If it still shows the untrusted developer message, force-close it by swiping up from the app switcher, then reopen it.
What If the Certificate Is Not Showing in Settings?
This is a common secondary problem. You see the error but there is nothing to trust in the Device Management section. Here is why this happens and how to fix it.
The Installation Did Not Finish Properly
If the install was interrupted or the app never fully downloaded, delete the app from your home screen and reinstall it through Scarlet iOS. Wait for the installation to fully complete, then check Settings again before opening the app.
Your Device Date and Time Are Incorrect
Certificate validation is time-sensitive. If your device clock is wrong, iOS may silently reject the certificate without showing it in Settings. Go to Settings > General > Date & Time and enable Set Automatically. Then reinstall the app.
You Are on a Restricted Network
Corporate or school Wi-Fi networks sometimes block the Apple servers that validate developer certificates. Switch to mobile data or a personal hotspot, reinstall the app, and then attempt to trust the certificate.
Trusting Multiple Apps From Different Certificates
Each developer certificate must be trusted individually. If you have installed five apps and each came from a different certificate, you will need to go through the trust process five times. However, if multiple apps share the same certificate, which is the case for apps installed with Scarlet iOS’s shared certificate, trusting the certificate once covers all apps signed with it.
To check how many certificates need trusting, go to Settings > General > VPN & Device Management and count how many entries appear under Developer App or Enterprise App. Each one needs a separate trust action.
Recurring Untrusted Developer Errors: Free vs. Paid Certificates
If an app stops opening every few days, it was probably signed with a free Apple ID (AltStore, Sideloadly). Apps signed that way expire after seven days and must be refreshed or re-signed; the trust you gave your own Apple ID usually stays. With Scarlet iOS, a recurring trust prompt usually means the certificate was replaced after a revocation.
- Free certificate: apps signed with a free Apple ID must be re-signed every 7 days, and on iOS 16 and later they also need Developer Mode.
- Paid/enterprise certificate: Trust once and it lasts until the certificate expires (typically one year) or is revoked.
- Revoked certificate: Apps signed with revoked certificates cannot be trusted regardless of what you do in Settings. You need to reinstall via Scarlet iOS using a fresh certificate. If Scarlet itself no longer opens, get it again from our Scarlet iOS install page.
If apps keep crashing or refusing to open even after trusting, check our comprehensive Scarlet iOS Not Working: 10 Fixes for Common Issues guide for a full diagnostic process.
Where the Setting Is on iOS 17 and Later
From iOS 17 on, the trust setting is in the same place:
- Open Settings
- Tap General
- Tap VPN & Device Management (it appears near the bottom, above Transfer or Reset iPhone)
- The certificate will appear under Enterprise App or Developer App
If you recently updated to iOS 27 and started seeing this error on apps that previously worked, check VPN & Device Management and trust the developer again if needed. Scarlet is confirmed on iOS 14 through iOS 26; iOS 27 support is reported by third parties but not officially confirmed.
When Nothing Works: Nuclear Option
If you have tried every step above and the app still refuses to launch after trusting:
- Delete the app from your home screen (this also deletes its data, so back up anything you need first)
- Restart your iPhone (hold side button + volume down, slide to power off)
- Open Scarlet iOS and reinstall the app fresh
- Do not open the app immediately. Go to Settings and trust the certificate first
- Then launch the app
This clears the error in most cases where the certificate is still valid. If every Scarlet app fails at once, the certificate has probably been revoked; see what to do when the certificate is revoked.
Summary Checklist
- Go to Settings > General > VPN & Device Management
- Tap the certificate name under Developer App or Enterprise App
- Tap Trust, then confirm
- If no certificate appears: reinstall the app, check your date/time, switch to mobile data
- If apps stop opening every 7 days: they were signed with a free Apple ID; refresh them in AltStore or Sideloadly
- For persistent failures: delete, restart, reinstall, trust before opening
The untrusted developer error is a built-in iOS security feature, not a flaw in Scarlet iOS. Once you understand the trust workflow, it takes less than 30 seconds to clear. If you run into any other issues during your sideloading experience, Scarlet iOS has the tools and resources to keep your apps running smoothly on any iPhone or iPad.