Hi Austin! Thanks for your thorough reply.
I’ve tracked this down to the WordPress 5.5 update that apparently “depreciated” calls to jQuery. This has subsequently broken many functions of many plugins and general WordPress backend (Dashbord) administrative functions – depending on what themes you have active.
I am using TwentySeventeen 2.2, which has a new release of 2.4 which may fix this problem, but I didn’t immediately update the theme because I have a customized version.
To fix this error and many others, I did find a solution recently (sorry I didn’t yet update this post as I just figured it out) with a plugin called
jQuery Migrate Helper.. it allows those calls to go through. Upgrading the theme might also fix the problem. Here is more information about the fix that may help with other people you are trying to help that have had problems with WordPress 5.5 breaking all of their plugins…
https://www.ads-software.com/plugins/enable-jquery-migrate-helper/
Thank you so much for your help.