This was an issue that cropped up in the last few days and was also mentioned by one of the ST staff members that affected several different thermostat dths, not just Nest that contained certain capabilities that for whatever reason GH didn’t like when linking accounts and they stated that they were going to create a bug fix for it, but modifying the DTH to remove those two things, linking to GH and then adding those two things (heating and cooling setpoints or something to that effect) back in after GH is linked. I didn’t explain it to you because you already had support uninstall all of NST Manager.
I totally understand your frustrations. We all go through things here that make us want to pull our hair out at one time or another.
Anyway, go back and check those specific things. 20 or more people have had the same oops issue and 9 out of 10 times it’s one of those issues I mentioned. It’s very very picky and sensitive. If you get it going, let us know in the other thread and if you are still having issues, post those screenshots over there. 
FYI: Here’s a link where the issue between thermostats and GH got some traction and was identified last week: