APC SMX1500RMI2UNC connect battery

I have a brand new APC SMX1500RMI2UNC which I installed last night.

All was good and running well last night. When I woke up this moing it is beeping with an error saying connect battery.

So I reseated all the battery connections in it and the additional battery set. The alarm was still beeping.

Unplugged the power cord to the unit and the system immediately switched to batteries. Plugged the power in and system retued to normal.

Left it for a few minutes and it started beeping again with the same condition.

The instructions do not indicate anything additional required to get the unit operational.

Can anyone suggest why this would be happening on a brand new unit?