I was just on the phone with HRB for a little less than an hour. I was having similar problem with both 2018 and 2019 Business (no problems with earlier years). I had uninstalled and reinstalled multiple times before calling support who had me do this as well. The software would install "successfully," but then the application never actually completed a startup.
The solution was to go to c:\ProgramData\H&R Block Business\H&R Block Business 2018 and then rename DataStore to DataStore.old . (He asked me to find a Restore file in this directory but there was none). I then started up the program and it starts and runs fine, including importing my 2017 tax return. ( A new DataStore was created in the directory)
I repeated the same in the directory for year 2019 with same success (minus importing a 2018 return because I don't yet have it there).
I did not need to do anything at all with rolling back Windows updates. I'll be interested to know if this fixes any of the rest of you.
Best wishes!