Bosch battery stopped charging
Here are the indicator lights and reset procedure straight from my Bosch e-bike training manual.



Voltage from the charger should be 5V so that doesn't seem to be the problem (See if it matches up with what is printed on the charger (either you have the 4 amp or 2 amp charger)).

The battery does have a built in management system (BMS) that safeguards against overheating, overcharging, short circuiting. As per the picture, you need to hold the button for 15 seconds to reset the battery, not the 10 seconds you wrote about. When the battery is critically low and gets recharged, you will need to do that reset.

I would recommend going into a Bosch certified shop if that doesn't work as they will have the dongle and access to the diagnostic software.