I had similar issues:
Before upgrading the firmware, my Android would connect via Bluetooth to the AMP75, but when trying to load/find tones i would get "token invalid". After spending ages trying to figure out how to upgrade firmware (done in the end using an iPad), i cannot connect my Android to the AMP75 via Bluetooth.
Not happy thus far if not working in a week or so i will be taking this back and getting a different AMP.