Hi there,
This is a known issue with some hosts that we’re planning on fixing in GP 3.2.0: https://github.com/tomusborne/generatepress/issues/325
However, there’s no need to downgrade. The links you’re trying to click are simply shortcuts that go to “Appearance > Customize”. You can simply click that link in your Dashboard menu instead of the links inside the GeneratePress Dashboard.
Let me know if you need more info 🙂