Anyone else have an issue where their battery won't charge? Polarity was always correct and the battery was charging without fail for some time, and now it is not charging at all. I replaced the battery, just in case that was the issue, but it is not. The controller ran of whatever charge the new battery had, but will no longer charge it.
Could you post pics of your old and new battery and controller? It may help to find any clue or something to solve.
Does BAT LED(right one in the pic) turn red(orange) when hooking up to USB? It should appear orange(green+red) during it charges battery.
If USB power line voltage is low it won't be able to charge battery. Try some USB ports directly on PC.
It is possible that battery charger chip is broken for some reason. I had a few users that burned battery charger chip with connecting battery in reverse polarity. For other scenario, the chip stands only upto 7V accroding to its datasheet and I wildly guess some AC adapter with USB port for phone and bad Type-C cable may supply high voltage. Though, I've not heard that case so far.
Did you use Type-C port or AC adapter for charge at some point perhaps?
EDIT: For future reference, using decent Type-C cable and 5V AC adapter with the bluetooth controller is safe, of course.