add -no-fonts -no-data to shortcut of the application as shown in picture.
Completely delete the files and reinstall it, must perform a restart. if it doesn’t work do checkout Error Log: You could check in GIMPPortable\App\gimp\bin or somewhere in data. You can also check the error console. If you don’t mind storing settings locally (just foe now), you can run GIMP directly in that bin directory to ensure it isn’t an issue with the portablization then later delete the .gimp directory in USERPROFILE