apc bv650I-GR

APC BV650I-GR continuously beeping after ~20 minutes of gaming — is this normal?
I recently bought an APC BV650I-GR (650VA/375W) UPS because I’ve been having some electricity issues at home. My lights sometimes dim and the AC has turned off unexpectedly, so I wanted a UPS mainly to protect my PC and give me enough time to safely shut it down if the electricity cuts out.
I connected only my PC to the UPS (no monitor, no PS5, or anything else).
I started gaming normally, and after around 20 minutes, the UPS started beeping continuously. The PC was still running.
The UPS was brand new, so I’m wondering if the battery needs to be fully charged before using it, or if the continuous beeping indicates an overload, voltage fluctuation, battery issue, or something else.
My main goal isn’t to keep gaming during a power outage — I just want the UPS to give me a few minutes to safely shut down my PC.
Is this normal for the BV650I-GR? What could cause the continuous beeping?