Replaced battery - icon shows black now

Hi guys, I ordered a battery from here and some flux for my 5th gen touch. Replacement went super easy. When I first powered it on it showed green in the gauge.

Per the instructions that came with the battery I drained it and then plugged it in overnight to charge to calibrate it. When I got up this morning the bar was full and it said 100% charged. When I unplugged it the level indicator went all black like it’s empty.

It’s working fine and so far this morning has 10 mins usage and 1 hr 42 mins standby since I unplugged it.

I’m planning on selling this but I’m sure I won’t get as much for it if the indicator isn’t working properly. Any ideas how to fix this? Thanks!