Good evening Stephanie and welcome to the Events Calendar Support forum!
Thank you for reaching out to us.
We are sorry to hear about the tickets not being sent. Yikes!
I would love to help you with this topic.
Normally, in such a case, simply using a plugin to send emails using an SMTP server does the trick.
However, I am noticing that you already have such a plugin in place. Furthermore, it seems to be properly configured since other emails are being sent.
At this point, I would exceptionally like to offer to login to take a look (not to touch).
For that purpose, I will require temporary admin credentials in a private reply.
Additionally, would it be possible to run a quick test to see if this is also the case when using a different payment gateway (e.g.: cheque payment) ?
Hang in there!
Geoff B.