I just had some success with this error this morning, combining a few suggestions found here. In my opinion, it's partly QB problem and partly a MS update issue. What I did that worked in my case was:
1) Edit the windows host file (found in C:\windows\system32\drivers\etc) to include the domains displayed in each of the error messages shown when opening and closing the program. For me, the below lines are what I added to the bottom of the file, but the domains may be different for you..
127.0.0.1 cdn.optimizely.com
127.0.0.1 tags.tiqcdn.com
127.0.0.1 s.go-mpulse.net
127.0.0.1 qbdtipd.qbinproduct.intuit.com
2) Open cmd prompt and ipconfig -flushdns
3) Look for the windows KB5003637 (June 8, 2021) update in your windows update history, if it's there, uninstall it and wait for the process to complete/restart.
4) Be sure to restart your computer after the update.
Note: Since this worked for me and seemed to have something to do with a windows update, I temporarily disabled windows updates with the hope that in 30 days or so, it doesn't come back and that either QB or MS will get to work and come up with a permanent solution for people.
Hopefully this helps..
