on my 2013 macbook pro 2019 catalina RIGHT CLICK on mouse NO longer works!!! it did until now

What mouse do you have? Make sure it's charged or has fresh batteries.

Have you checked the System/Mouse/Point & Click preference pane? You might want too toggle the Secondary click checkbox off and on a couple of times.

Log into another admin user account, Set up users, guests, and groups on Mac,  and see if the problem persists. (This tells us if the problem is limited to your user account or is system wide).

Next, boot into Safe Mode (How to use safe mode on your Mac - Apple Support) by booting with the Shift key held down and check there to see if the problem persists.  Reboot normally and test again.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing some system cache cleaning, volume verifying and directory repairing. 

It's most likely to be a faulty mouse! Can you test it with another one?