Not sure if this helps you guys, the following is the error thrown in console
Uncaught Error: No select2/compat/dropdownCss
Screenshot: https://imgur.com/a/8AyV3hk
Googled it and found this reference – https://github.com/select2/select2/issues/5854
Hope this helps!
I am having problems with this plug-in as well. Never had a problem with it until today.
Thanks Harvey for documenting you process of getting the Gravatar plugin working. You saved me some time and I appreciate it. Thanks again!