Sending registration code via gmail is being blocked

Your post offended the spam filter due to the many links, sorry. I removed most of it to make sure it stays.

In regard to your actual problem I can’t say much unfortunately. If you maybe have some mail forwarding to your own server configured in Gmail that’s probably the issue. Just a wild guess though, other mails from Gmail arrive without problems.

Anyway: As an alternative use the contact form (Support > Contact in the menu above), although it says to not send key requests that way. Will take a bit longer since the license server can’t respond to messages sent via the form automatically, but I’ll make sure your key is sent manually.