You say “latest” – just what version is that?
From your description, it sounds like you’re not actually encrypting with AxCrypt (portable or not). You are aware that the portable AxCrypt 2.x does require you to use the AxCrypt main window? There is no explorer integration. If you do try to encrypt from the windows explorer context menu, you’re probably accessing and using the built-in Windows EFS encryption (which is very non-portable, since the encryption essentially is tied to the user/windows pc it was run on).