Hello there, Robyn! Welcome back to the forums and thanks for getting in touch. 🙂
Would it be possible for you to open up the Community Events form to anonymous visitors so I can take a look and see what’s happening? Right now, the form requires an account.
Without looking at it, the sounds like a Javascript conflict. I know you said you tried deactivating all other plugins (which is great!) but I wonder if there is a conflict with the theme that’s throwing that conflict. I’ll be able to see that when the form is opened up, but it would also be great if you could try switching to a default WordPress theme (like Twenty Fifteen) while deactivating other plugins to see if that makes a difference.
Let’s start there and see what we find. 🙂
Cheers!
Geoff