Now I feel kinda stupid. I re-installed Audacity using the pkg manager. I tried opening a file in the HD folder by double clicking on it. This resulted in a message that said that file was made with a later version than the one I had installed, which was 3.4…something.
So, I booted up W11, and found that my Windows install was 3.7.7 - Hmmmm….
Re-booted Zorin, went directly to Audacity website, and got the lates Linux version which was…3.7.7.
I installed it, and it works exactly like I want, opening the existing files no problem, so it appears it was a version issue all along. Sigh…
Thanks to all who were offering suggestions!