Simple setup but authentication fails when accessing remotly

I have a basic setup of Rebex SFTP on an active Windows server 2022 standard. It's a simple server setup running AD. I have Rebex set up with the local server IP address as the listening address on port 22. I have set my firewall to use a dedicated static IP address to NAT forward all data to that server (I'll change that later for security reasons.) When I use an SFTP client in my environment to connect to the SFTP server using its local IP address the connection works but when I use the external IP address the connection is established and the certificate is shared and it accepts the username but when I enter the password it says "access denied." What am I missing? Thanks!