Znen ZN50QT no current

Hello in the round, now my mofa has been standing for quite a long time and it would be great if you got it to run again somehow. A short history: At first it was really good and very reliable. But at some point the first bitches came out. First the E-starter failed, which disturbed me especially, because he let himself compete without any problems. But then the first dropouts came during the ride. Somehow, as if he didn’t get fuel. That was always short, but was quite last ig. At some point he stopped me while driving and he didn’t let himself compete anymore – why ever. I checked the fuse, which was ok. I connected the battery to a charger and it would have to be full. But if I plug in the ignition key and turn nothing does, nothing at all. So also the display devices, such as fuel level, didn’t make a sound. Does anyone have an idea? If still an information should be needed, just ask. I might not be able to execute it. H enough to describe – I am really not an expert and do not know what is important in the question. Thank you, dear greetings, Georg