Hi Lee,
Thanks for getting in touch. It sounds like the issue you’re having has to do with the permissions set within the WordPress dashboard itself. Particularly since the calendar was working previously, you might want to check to see if the user roles or other permissions were altered.
Also, since your client is running such an outdated version of the calendar, we really can’t provide much in the way of support. The current version is 3.0, and we have both the free core plugin, The Events Calendar, and our premium add-on, Events Calendar PRO. If your client wants to continue using the calendar, I highly recommend that you update to a more recent version.
Best,
Leah