Every couple of months my 2019 Word and Excel stop working on Catalina. I have reinstalled both the OS and the microsoft program multiple times. Any suggestions? The iMac is less than 1 year old.

That may be your problem. At best it is 100% useless, the best antivirus, cleaning, security and overall maintenance app for Mac OS is Mac OS itself. We see users everyday that are complaining about weird problems with their Mac and most can be traced back to apps like Bitdefender. These apps have the exact opposite effect users anticipate, they make Mac OS slow, unstable, get odd behaviors, and exhibit issues like you are experiencing.

Please locate the developers uninstall instructions and please uninstall Bitdefender. Then test and I suspect your issue will be resolved.

Please contact the Microsoft hosted forums for the Office for Mac.

By chance, do you have any third party antivirus, cleaning or any other third party maintenance apps installed on the computer?

+1. Also, you do not tell us exactly how the apps "stop working". In order to help you, you need to help us by providing specific information for us to respond to.