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iOS shows this alert when you open an app that Xcode installed with your Apple Account, such as WebDriverAgent’s runner:
Reports quote this wording from iOS 15 (2021) to October 2026. Older iOS versions said the developer has not been trusted on this iPhone. On the Mac, xcodebuild and xcrun devicectl device process launch report:
devicectl wraps that line in ERROR: The application failed to launch. (com.apple.dt.CoreDeviceError error 10002 (0x2712)) and The request was denied by service delegate (SBMainWorkspace) for reason: Security. Xcode’s own alert calls it Developer App Certificate is not trusted. When the helper hits it, Mobster for Mac shows Trust the helper app on your iPhone: open Settings › General › VPN & Device Management, with a picture of that screen. Within 10 minutes of the failed start, mobster doctor prints a ✗ beside Phone connection with doesn't trust the helper app yet and the same steps.

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Why it happens

The developer that signed the app isn’t trusted on this iPhone yet. Appium’s provisioning guide describes it for free Apple Accounts, which Xcode lists as a Personal Team. A report on Apple’s forums (2021) shows it for a paid team’s build too. Mobster can’t trust the developer for you: only you can, in Settings on the phone. The xcodebuild line has a second cause. When a free account’s signature expires after 7 days, iOS refuses the app with the same sentence. Mobster checks the signature’s date before it reads the sentence, so it tells the two apart.

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Fix

  1. Tap Cancel on the alert.
  2. Connect the iPhone to the internet. iOS checks the developer’s certificate with Apple when you trust it.
  3. Open Settings › General › VPN & Device Management.
  4. Under Developer App, tap the entry with your Apple Account.
  5. Trust the developer, then confirm. In Appium’s provisioning guide the first button reads Trust with your Apple Account after it, and the second Allow.
  6. Open the app again. For the helper, choose Try again in Mobster for Mac, or wait: Mobster starts it again by itself.
If iOS says An internet connection is required to verify trust of the developer, connect the iPhone to Wi-Fi and try again. If the developer is listed with no Trust button, a report on Apple’s forums for iOS 15 fixed it with a new certificate: Xcode › Settings › Accounts › Manage Certificates › + › Apple Development, then install the app again. If the developer is already trusted, the signature may have expired: see the runner’s signature expired.

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Check it worked

The app opens. For a regular app, xcrun devicectl device process launch --device <UDID> <bundle id> launches it with no Security error. For the helper, mobster doctor prints a ✓ beside Phone connection. See also Invalid code signature. Checked 5 Nov 2026 against Mobster 0.4.0. Back to Troubleshooting.