Tentacle Sync Battery Doesn’t Charge

Hey all,
I’ve recently started experiencing this:
I plug in my tentacle to a usb charging source and the green light starts to blink as usual. However the unit is no longer absorbing charge and when I check voltage via the app on my mac I see the charging meter ping-ponging between multiple voltages while not gaining any charge toward full. I have left the unit plugged in multiple times for a duration that should have guaranteed a full charge and it still is not working.

Has anyone experiencing this and have any tips for what could be going on?

Thanks!

-Nick