Twice now my Ring alarm pro has “lost power” and gone into back up mode while still plugged in. The only way I found to wake the alarm up is by powering the system off and on. Alarm is plugged into an APC UPS , and power to the house has not been lost. Because the Pro is required to be the main router (bad concept!!) I lose all network connectivity when the battery runs out. Being powered via a UPS, this unit has never lost mains power.
Not all electronic devices like being plugged into a UPS. Try without the UPS and see if that makes any difference. If it doesn’t reach out to Ring Support for troubleshooting options.