I got the 70001 error message in april 2020. I followed the previous instructions by rebooting my PC. After 2 attempts, it worked and I was able to get to my returns.
Both TT business and TT home and business then went straight to updates. They both updated correctly and I was able to continue my returns.
Don't give up hope, I think you will be able to get it to work, it only took 20 minutes to get back up and running.
