I had problems as soon I as purchased 9.5 for my Windows 10 Intel I7 PC with 16 gigs of ram.
I was first told my dongle might be the problem so I bought a new dongle as first one was pretty old.
I then talked to tech support. I tried going into User, AppData, Steinberg file and deleting the files there. I had to recreate my settings in Cubase, but the good news is it worked.
However days later I am getting the same problem going into Cubase 9.5. I have no problems going into 8.5. So this tells me this is a bug in the new version. Hopefully they can fix it. I tried the Elicense Controller and updating things there but I would say at least 60% of the time when I try I cant get in.