“Unable to connect via TLS” with Mailgun

Hi! Love your plugin.

Trying to discover why we started getting “Unable to connect via TLS” with Mailgun recently, although Mailgun doesn’t report any problems.

You getting this message because an error detected while delivered your email.
For the domain: https://www.uubrunswick.org
The log to paste when you open a support issue:
Unable to connect via TLS

We ran the wizard again with no connectivity issues and the test email went through just fine.

We searched in the support history for these topics without success.

Any pointers to similar problems, resolved?