If you’ve deleted that internal SketchUp web browser cache folder (make sure to delete it for the version of SketchUp you are actually using) , it wouldn’t do any harm to delete the login_session.dat file there too if you have one.
I’d be looking towards firewalls,vpns, ad blockers that affect the whole system.
does the page show in a normal web browser?
It’s the main login page for any SketchUp/trimble page