Is my Microsoft Universal Mobile Keyboard battery dead?

invalid@example.com (Goi), Goi
Sun, 07 Apr 2024 04:46:29 +0000
Keyboards

Hi guys,

I inherited a MS UMK Bluetooth keyboard, and charged it overnight. I then unplugged it and tried to pair it, but my Android phone couldn't detect it. I plugged the USB cable and tried again, and it was able to pair this time, and I was able to use it. However, once I unplugged the cable, it stops working.

I've googled around and didn't get anything useful. Some say the charger may not be compatible, but if so, why would it work while plugged in?

What else could I try before concluding that the battery isn't able to hold a charge anymore?

BTW the unit looks brand new so it doesn't look like it was used much at all.