It won`t charge but It can only use Battery power.
I have the same problem.
I didn't use mine for like one year and switched it on today.
Suddenly the circuit breaker turned off and once I turned on, the UPS stopped charging on A/C power but runs only with remaining battery power.
I think the PSU of my desktop got malfunctioned after the circuit breaker disconnection incident.
UPS : APC 650VA
Power Supply of the Desktop PC : Raidmax 500AF