Thanks for this comment relating to the hard reset.
My daughter (8) soldered most of the board. When she was playing around with it, when we made it work, i guess she was interrupting the loading and thus left console display blank. I’ve been nearly de-soldering the whole board’s components.
Fortunately I found this posting here. Now it’s working again. Thanks!
Maybe the hard reset info should be part of the assembly documentation. I’ve found no such info there.
Cheers from Germany,