The SiteGround gus had this to say.
Thank you for the update, Al.
Your website indeed is working properly via HTTPS now, and I was able to
successfully place an order without any issues or errors – here is a
screenshot:
http://prntscr.com/efp9xn
Regarding the error with the plugin, I have searched the web and found
following thread:
https://wordpress.org/support/topic/cannot-connect-to-eventbrite/
It suggest re-checking the settings and the URLs set on the plugin and the
website, so please, check that again:
http://automattic.github.io/eventbrite-api/users.html
The developers of the plugin will know best whether the issue is related to
some of the settings, or is different one.
In case there are any actions required from our end, let us know and we
will gladly help.