Hi Edward,
Thanks so much for reaching out!
I’m sorry to hear that you are experiencing this issue on your site!
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/
If you go to Events Settings < Licenses, do you see Valid Key under all of your licenses?
I would recommend removing the keys and re-adding them in.
Then flush your permalinks by going to Settings < Permalinks and Save Changes.
Let me know how it goes!
Thanks,
Jaime