very interesting finding!!!
I ran the command:
upsdrvctl -d stop
then:
upsdrvctl -d start
another words, restarted the service
and then
upsdrvctl -d shutdown
and it worked!! the ups moved to “power loss state” for about 1 minute, and then powered off completely. Then powered on in 5-10 seconds itself because it detected input voltage, server started.
very strange