Thanks shreeswifty & oweno for the reply.
So, as many others I ejected rejected it a lot of times. And of course I had to when I mounted the new firmware on .
this is a good hint. I used a “third party” power adapter, but it should work - all needed parameters are identical.
However, I’ve to buy an adapter because I’m staying in Germany and the included one isn’t for our power plugs.
I hope it will work, otherwise I’m more frustrated because of spending more money for nothing (Btw, a great song…).
Will do that next week and report if this helped.