Hello ***++Łukasz Zakrzewski,++***
Have you tried switching the battery with another one. Or have you check the readings of the battery with a volt tester?
Recommend disconnecting the battery. Then hold down the power button on the switch for 30 seconds. After plug-in the battery and check if the switch charges.
If this doesn't work, you could have a bad battery.
Hope this works for you.
P.S. let me know if it works for