Hi,
it needs some time, but now I found the root cause and the Digi-pro is running!
And to my shame it was so simple at least, that I'm a little bit anoyed of my stupidity. It was a mechanical thing, means I haven't mounted the HAT deep enough on the GPIO plug, what I didn't recognized, because I put all together in a self adapted case and the assembly wasn't easy at all and I don't wanted to dismount again.
So, thanks to all, which tried to help me and hope they are not to angry wasting there time.
With regards
Sindbad6