A few days ago there was a power outage. When it came back, the circuit breaker where my UPS was connected tripped, and when I re-armed it, I realized that my UPS was no longer working (the connected devices were no longer powered), and was making a continuous beep.
Trying unplugging it from main power, plugging it back in, and plugging it back in again, the green light flashes for a few seconds, then a relay-like sound is heard, and the continuous beeping begins, with the green light continuing to flash.
The UPS most likely took a voltage spike and an internal component has failed. You should replace the UPS as none of the internal components are considered user replaceable. If the UPS is under warranty please contact local support and they will be happy to assist with a warranty replacement.
Local support contact information will be found at this link.