Failure of new charger and unable to diagnose

I am English and in the UK. I own a Twizy 2017 imported from Korea with the Nilsen battery installed about 4 years ago by his UK agent. The Twizy failed 2 years ago with the charger malfunction symbol. I installed a new charger from Renault myself. I am 81 and have no electronic or EV experience.
Result is: the charger does nothing when I connect it; in key position 2 the 12v accessories work; the battery shape flashes: there is the written ERROR; there are the 2 horizontal bars; the STOP and SERV lights are illuminated; nothing changes when I turn key to position 3 (normally N).
I have a new dongle from Kenneth. The 12v battery is externally charged fully. The installer here refuses any help. Kenneth sent me a canbus adapter but I have no idea how to use it. He may or maynot visit me in England. ihave failed with an OBD diagnostic reader.
I have 3 chances: 1. someone can sort this out. There seems zero chance I can get this help. 2.I can somehow check if the battery and BMS are good I could use them in an old Working 2012 Twizy with low battery. 3. If anyone from Germany, France wants to come here and take this Twizy for spares/repairs complete I will not ask for payment and will provide UK document.
With many thanks for all the information provided by you people, but despite many hours reading I am defeated. Apolgies I have no German, only Spanish and French. I am located near the famous 'Stonehenge', Wiltshire, England.

Hi.

Welcome to the show!
First, it is very important that "we" find out what error messages are in the error memory.
To do this, however, you need to get an OBD2 dongle up and running, and the corresponding software. We will help you with that.