Hey Joy,
Sorry to hear that you’ve run into this issue!
Do you have FTP access to your site? If so, I would recommend temporarily removing the existing Event Tickets Plus plugin from your site. You can then log into your dashboard and update the core Events Calendar and Event Tickets plugins to the latest versions.
From there, you can download a fresh version (sounds like you may have gotten a partial update on the Event Tickets Plus plugin) of the Event Tickets Plus plugin from your account here https://theeventscalendar.com/my-account/downloads/ and upload it to your site.
Let me know if this helps.
Thanks!