XMPP/Prosody not working for external clients

Hello all,

We are having an issue with Prosody in FreePBX Distro 10.13.66-6.

Anyone outside the LAN is unable to connect to our Prosody (jabber) server. We have already opened ports in the FreePBX firewall (also tried disabling firewall entirely). The outside clients are connecting via VPN (both Site-to-Site and SSL). I can telnet into the following ports from the client machine that is affected: 5269, 5222, 8088, 8001.

When connecting via the Spark client, it gives an invalid username or password error. That same user authenticates correctly from inside the LAN.

Does anyone have any suggestions?