TranzX 36V

If it does not charge, it can be reset by charging from the discharge. See photo for layout:

Changing the button

If you cannot see anything on the indicator, it can be because the button is water damaged.

To have access, you must carefully peel off the sticker. There are two screws to undo under the sticker. Then, you must pry to get the plastic cover out and expose the indicator board.

The button can be changed to identical using the hot air rework station.

The sticker and the screws:

Shorting the terminals of the visibly corroded button:

Victory - it is the button!