Good evening Suzanne and welcome back!
Thank you for reaching out to us.
We are sorry to hear about the fact that you are unable to associate a Venue or an Organizer with an event.
I would love to help you with this topic as this is definitely not normal behaviour!
As a first troubleshooting step, could you please provide us with your complete system information in a private reply using the instructions found in the following link?
https://theeventscalendar.com/knowledgebase/sharing-sys-info/
It sounds like there might be some type of conflict at play (but I won’t know for sure before getting the system information).
In the meantime, here is something I would recommend.
After a backup and preferably in a staging/dev environment or local clone install of your WordPress website, could you also please go through our testing for conflicts procedure and let us know what you find out ?
At the very least, it would be good to quickly and temporarily switch back to a default WordPress theme to see if the issue persists.
Best regards,
Geoff B.