I believe you need to add the serial # of Myq 821LM device to register it with ADC.
MyQ devices are added through the Alarm.com website via Settings -> Automation Devices -> LiftMaster Installation.
Records indicate that a LiftMaster Hub and door are currently associated with your account.
MyQ devices are somewhat unique however. Should a Second MyQ hub be added to an account, only the dealer (us in this case) can enable it. Should this be the case, then the serial # of the second gateway would need to be sent to us. This can be done via the Secure Message Tool, for account verification purposes.
Additionally, the removal of MyQ hubs can only be done by the dealer as well.