If you are unable to enable/disable Remote Access and see a message stating that your "AmpliFi is registered to another account", you can fix this issue by logging into the WebUI and removing remote access there. Once removed, you can start from scratch, and enable it again on the mobile app.
1. To access AmpliFi's web interface you must be connected to the AmpliFi network on your computer.
2. Open a web browser and in the URL bar type either http://amplifi.lan/ or the router IP address.
3. To log in, use your admin credentials: the same ones you would use to log into the AmpliFi mobile app. If you do not know your admin password, but have access to the app on your mobile, you can change the password without resetting it by following the instructions in this article: Changing your Admins Password.
4. Once you have accessed the webUI, navigate to Support > Tools and remove Remote Access. Save changes and now go enable it in the mobile app.