Try closing all Arduino IDE windows and then start the Arduino IDE and try again. That will clear the cache and hopefully fix the problem.
I all ready tried resetting the IDE with out any luck
Let's stick with that as it is a short program.
Post the exact error message that the compiler produced when trying the Blink program.
Are you sure you have selected the correct board in the IDE?
Do you get a compiler error if you try to compile for an Uno?
This is the same error as before. Here it is again
Arduino: 1.8.5 (Windows 10), Board: "Adafruit Feather M0"
GetFileAttributesEx C:\Users\Rocke\AppData\Local\Temp\arduino_cache_825726: The system cannot find the file specified.
Error compiling for board Adafruit Feather M0.
This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.
Yes I am using the correct board in the IDE "Adafruit Feather M0"
No I have not tried to compile for the Uno,