FTPS not allowing directory listing

 Hello,

  I'm trying to set up FileZilla Server on a server and I'm running into an issue.  Everything works fine internally, but when I try and access the site externally, I am able to log in but directory listing fails.  I an only imagine I'm missing a firewall rule but I'm not sure what it would be.  I have the following : 

Firewall : 

Any-->FTP-->Internal FTP Server

NAT

ANY-->FTP-->External FTP Address-->Change To Internal FTP Server Address

I set FileZilla to use Passive ports 50000-50050 but when I look in the Sophos logs, I don't see attempted connections within that range, the ports are higher.  I tried testing a firewall rule for 1:65355(Source) and 1:65355 (Destination) allow to Internal FTP server but it still wouldn't list.

Can anyone help direct me to what I'm missing?

 Thanks.