I opened TurboTax 2021 Desktop for reference information, it forced an update, reported an error, and now fails to open. How do I get help for the product I paid for?

What fails to open?  The program or your tax return?  What error message?  Is it error 190?  Did you have to reinstall it?  

After you get the program installed or reinstalled the first thing to do before you open your tax return is to update the program and install any state programs you had. Then open your file. So you first might need to start a fake return to be able to download the state program (go to File-New Tax Return).

Then go to FILE -Open and find your return.