[ @Barb Stapf]
After spending all night (at least 6-10) hours trying to get Excel to work and giving up, I posted the above comment. Then suddenly everything was OK. Not sure why or what happened. It’s possible Advanced System Care fixed it in the background, but you would think it would let me know?? I had already checked for updates and done everything I listed above multiple times, etc. I even spent a couple hours copying the original document to the new one which then didn’t work either. I hope this is behind me and never happens again. Even though I have never closed everything in the past, I will always close everything before loading any software in the future!!!