When I set up outside, I was still on mains power (both the PMC-8 as the laptop). The laptop was correctly connected to the PMC-8 via WiFi. I even switched to my normal internet-wifi signal and back again. It connected without any problem, but the ExploreStars application was stuck on "Please Wait". restarting ExploreStars several times had no effect.
Once inside again (I had unplugged the power to do that) and putting the power back on, ExploreStars started up normally with the compass-rose for slewing.
The distance between inside and outside is about 5 meters. That cannot be the issue.
One positive point was that clouds drifted in 15 minutes later (not forecasted by the nightshift app by the way, it promised clear skies for hours), so no precious observing time was lost.
I have the Exos-II / PMC-8 now since September 4th, and have had zero skywatching time with it :( So, forgive me for being less then jubilant.