I had the exact same problems. Everything worked fine with the first tips for months, when it comes to entering all the firewall rules manually and so on. Then one day, suddenly some Win 10 update or something messed everything up. I don't know. Tried to fix it what seemed to be a zillion times, in the end I tried to run the toolbox from a different computer. To my (not so) great surprise, everything worked just fine with the toolbox mf 17 version that Asia servers had published some time ago. In my frustration, I turned back to the broken PC and just ran some basic built-in Windows 10 troubleshooters. The first two options yielded no result. (Compatibility mode and one other (rather obscure) involving scaling/resolution I think.) But when the troubleshooter tried to run it as administrator (specifically), everything suddenly worked, for no apparent reason. Up until that point, I had been able to find my computer and get toolbox to load, but none of its buttons worked until the admin was in the seat. All of this should not be necessary, the first tips in this thread worked just fine until a few days ago. I use my scanner regularly. The problem just came into existence out of seemingly nowhere.
Hope running as administrator works for someone else as well.