Xcode 12.3 beta: Failed to prepare device for development

A simple phone restart will fix it

I have had to come back to this SO question twice in the past couple weeks. First time, I did have to update my Xcode and iOS versions, which fixed the issue. Now, the issue has returned, but there are no updates. I tried disconnecting and reconnecting my phone from my laptop, but to no avail.

What fixed it the second time was merely restarting my phone. I am curious if that would have fixed it the first time too, without needing to have updated.

I know this is just echoing the other answers here, but at the very least, I would recommend just starting with a simple phone restart and seeing if that fixes your problem. Here is the specific screenshot that I encountered, in case yours is the same (pro tip: you can open up the "Devices and Simulators" window by going to Window -> Devices and Simulators).

Errors were encountered while preparing your device for development. Please check the Devices and Simulators Window

Exact same problem here, this solved the issue for me:

  • Delete the app from the phone
  • Clean the Build Folder with: + shift + K
  • Delete derived data
  • Unpair device (from + shift + 2 window)
  • Disconnect iPhone
  • Restart iPhone
  • Restart Mac
  • Trust

After this, it worked for me.

I restarted my iPhone(14.2); now both Xcode 12.3 beta and 12.2 can run app on my device.