Hey !!

Installed theme
Setup email server (private Settings)
Sent test email (Perfect, worked)
.
But, Will not send email at all using website
a. Register
b. Send to Friend (Share)
c. Forgot password

Gmail settings do not fix the issue.
Internal emails work ie: Tests, New User signup alert

It's ashamed too. We advertised this website knowing that the test email worked, so we did not go any further.
No user can register, because they do not receive the confirm email...

Please advise, Could it be Theme? Backend Theme?
Server: Apache

That sounds like mail server issue.
Try to review/test ports, ssl verification, ...

OK...Found the issue !!!! It works now !!!

Installed was PHP8.0 which OSC claims to support??
Changed to PHP7.1...all emails work now.

Php 8 works ok on all our servers, but there could be some dependency on your hosting or simply php mailer library is not perfect on php 8