If you see ODU Comm Alarm on PTP810 this indicats that there is an issue between the Modem Chassis and the ODU.
This could be a hardware fault, but before returning hardware please check the cableing between the units. Check any other devices in the IF cable are functioning and installed correctly - For example any Lightning Protection Units (LPU) and grounding kits.
A test should be conducted between the Modem and the ODU with a known good cable before any RMA is initiated.
If the problem persists, please contact Cambium Support to investigate further.