Hey Marie,
Thank you for reaching out to us!
I’m very sorry about this issue you are experiencing, let me help you to solve it!
Can you please make sure that both The Events Calendar and Events Calendar PRO are up to date? After that, please access your Dashboard and head over to Settings -> Permalinks for a permalink flush (no need to change anything, just visit the permalinks page: WordPress will automatically flush your permalinks once you visit it).
Don’t forget to clear your site’s cache and your browser cache after this change.
Let me know if this helps to solve your problem!
If you have any other questions in the mean time, please let me know and I’ll be happy to assist!
Best Regards,
Patricia