Fix predetermined install on external drive.

ok. try these other steps.

Uninstall and reinstall the game:

Uninstall MSFS 2024 completely.

Reinstall the game.

7. Try to fix the installation file:

On Steam, you can try to "fix" or "restore" the game's installation file, if available.

8. Check if MSFS 2024 is installed on the external hard drive:

Flight Simulator X may have issues if installed on an external hard drive

Fixed

I found that if it's installed on external hard drive just go to store and click install it reads the hdd and detected the game

Best option here would be to uninstall the game and then install it on the external hard drive. Should fix that for you then.

I've got the same problem. Tried all the troubleshooting fixes and it still doesn't recognise the external drive. The internal drive is full and all of my games are on the external drive so my Xbox One is currently useless. This needs a fix soon as I can't
play any of my installed games or use most of the apps.

There is a possibility that there is either a connection issue with your external hard drive or somehow the external drive is corrupted. One possible solution is to uninstall the game and then reinstall the game. Try installing the game on only the internal Xbox hard drive to see if that fixes the problem. Also, try launching other games on your external hard drive to see if how those games are functioning normally.