[Flutter] How to solve the problem when the build on the actual iPhone fails.

Seito Horiguchi
1 min readFeb 26, 2022

The other day, while developing an app in Flutter, I suddenly encountered the following error when I built the app to check it on my iPhone.

Unable to prepare iPhone for development.


iPhone is busy: Fetching debug symbols for iPhone. Xcode will continue when iPhone is finished.

I wondered why this was happening since I had been able to build without any problems up until then. I wondered why, but it seems to be an error that occurs when the iPhone OS or Xcode is upgraded.

The following are all the things I tried before I solved the problem.
To be honest, I haven’t been able to identify which ones were effective because I tried many things and before I knew it, the problem was solved.
If you’re having the same problem, give it a try! Any of them will solve your problem.

  • Run `flutter clean` and `flutter build ios` again
  • Wait 5~10 minutes and build again
  • Reset the trust between iPhone and Mac PC (Open iPhone -> Settings -> General -> Transfer or Reset iPhone -> Reset -> Reset Location and Privacy), then reconnect and trust again
  • Restart Mac PC
  • Restart iPhone
  • Manually delete an app built in the iPhone once
  • Upgrade Xcode
  • Upgrade your iPhone’s iOS version.