If you are using the RMail for GMail extension and the Send Registered button is not working. Please try the steps listed below to resolve the issue.
1. Log out of Gmail.
2. Remove the RMail for Gmail extension in Chrome.
3. Clear Cache in Chrome.
4. Reboot Chrome.
5. Add the RMail for Gmail button.
6. Log into Gmail. The Send Registered button should now be available
Send some test emails to yourself to verify that everything is functioning - if not please submit a support ticket and we will contact you.