Wii U Pro Controller won’t charge

I bought a pro controller off eBay and it came in today and was dead when it arrived. I plugged my PS3 mini usb cable into my switch dock and then plugged in the controller. It started charging fine so I went about my day and came to check on it a while later to find the charging indicator LED was off despite the controller not being fully charged yet. I unplugged it and plugged it back in and that seemed to do the trick, so I just had to keep doing this, but everytime I plugged it back in, the time it would charge before the light when off kept getting shorter and shorter until eventually I tried plugging it into a wall outlet using a phone charging block because I read online that can help with charging it. When I did this, the charge light flashed and it wouldn’t charge at all, and now when I plug it into anything that’s what happens, even the Wii U. The charging indicator blinks once really fast and turns back off and the controller doesn’t charge. I can however still use the controller directly plugged into the Wii U like a normal USB wired controller. When I do this, it looks in the Wii U menu as if the controller is charging even though it isn’t. If there’s any information you need that could help you help me please don’t hesitate to ask and I’ll respond ASAP. Thank you all in advance for the help :)

https://imgur.com/cxi4eZv

https://imgur.com/ceP4GyB