@Bryanvh I think I've managed to reproduce the issue. The fact that the master's certificate is missing from /etc/stunnel/certs-pool/ seems to be the problem.
On the master, run xe host-refresh-server-certificate host=$(hostname) and then xe pool-certificate-sync.
Then, if you run ls -l /etc/stunnel/certs-pool, you should see a certificate with the same name as your master's UUID. It should end with .pem. If it ends with .new.pem, I recommend copying the certificate, removing the .new (which can apparently cause problems).
You should then be able to join the pool from your host.
I hope this worked. Please let me know if it works.
Respectfully,