Hi Christine!
I’m sorry that you’re running into this issue, but I’ll be happy to help you get it figured out.
I see that you’re running the current versions of Event Tickets and Event Tickets Plus, but the version of WordPress that you’re running is quite a bit older. Can you first try updating to the current version (4.9.6) and see if that gets things working?
I would recommend making a full backup of your site and doing this update first in a testing environment, just to be on the extra-safe side.
Please let me know how this goes!
Thanks,
Jennifer