Trust UPS doesn't keep the PC up

Hi.
I have a Trust Paxxon 1500VA (which I understand is not at all top-of-the-line but that's what was feasible at the time of purchase), that I use on my desktop just as a measure of protection and to have the time to shut-off the PC in case of a power outage. Real light usage.

For the little less than two years I have had it, It has been serviceable, until it wasn't for no particular reason. Now if the power goes out (or if I test the UPS through ViewPower - another non-stellar software, I seem to undestand, but I'm not clear on good alternatives) the UPS stays on (green light) but the battery doesn't kick in at all, not even a little (it used to lightly buzz and beep, now it is completely silent), and the desktop immediately turns off. I've moved the wires around just to see if something changed, and it didn't, but all 4 outlets should be both battery and surge-protection anyway.

Now, before I go appealing to the last month-or-so of warranty, is there a way to check if something is actually wrong or if maybe I unchecked something via Viewpower (which I uninstalled and installed again, so I don't think that's the case) to make it not work?
This is the main screen from Viewpower, in case that could be useful. Battery seems fine, but I don't know if that's of any value: viewpower screen. I'm not sure about that 27.1 V since the batteries are supposed to be 12V, but I really don't understand anything about power matters and I have no idea if that's normal or not. Guess that's because there's 2 of them?

Thank you for any help you might give, and sorry if I'm such a knucklehead bout it.