I think I found the problem.
Using the .bat file provided in this thread: https://espmc-eight.groups.io/g/MOUNTS/topic/dhcp_static_ip_issue_with/77617950 does NOT work for me.
Everything seems to be set correctly when looking at IP addresses and so forth, but somewhere something is wrong.
When I change the network settings through the settings of the ethernet adapter (see image), then ExploreStars comes to life ! And I have no clue why ;/
I have tried to fire up ExploreStars 3 times from scratch, and each time I saw no trouble..
I will keep monitoring the situation and keep you posted.