Hey James,
Welcome back!
I’m very sorry about this issue you are experiencing, let me help you with that!
We recently changed the permalink logic for recurring events (it was removed from The Events Calendar and implemented on Events Calendar PRO instead), so to make sure that everything works as expected, please update both plugins to their latest versions.
If the issue persists after the plugins update, 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).
If the issue persists after the permalink flush, please let us know and we will be happy to further investigate your case.
Regards,
Patricia