Welcome to the A600GS forum

[balrog74]

I went through this recently myself (have had the A600GS for about a week), with my purchased Amiga Forever ROMs not showing up in the import list.
In my case I have an Apple Mac and can't run WinUAE, but found some decryption software here https://github.com/abcbarryn/decrypt-amigaforever?cmdf=decrypt-amigaforever.
It needs to be compiled and have the rom key file available, but worked perfectly.

[balrog74]

Glad to hear it's working for you now!
Incidentally, Nuclear War and Sensible Soccer are two games I have on my A600GS as well.