Charger does not start

Hello everybody, my battery is empty again and I urgently have to charge it tonight! Short form: car is moving little, stood now three weeks. Go still with remote control, interior lighting goes, amature display etc. everything goes. But when starting it does not give any sound of itself. So you can hear nothing from the engine. Charger from Lidl (NOT the whole new one from this week) attached to built-in and still connected battery. It flashes when making the power supply. the battery symbol of the charger and then the charger goes back to the standby again. With the only button on the charger (mode button) I can not switch between the individual charging programs back and forth. I just tested the charger on another vehicle (even with connected battery). This is fine. It was also guaranteed to be wired correctly (otherwise the “call sign symbol” would have lit up – this also extra with separate power supply again p Robes: as soon as the terminals are wrongly connected to the charger, the exclamation mark lights up) Does anyone have a quick advice? Is it worth to disconnect the battery? What can it be because it doesn’t start charging?