RDWeb and RemoteApp are working fine internally but not external

Hi,

I have Server 2012 with Remote Desktop Service installed

SSL is working fine. I am using StartSSL.

I am having problem with accessing RemoteApp externally. Everything is working fine within internal network. When I try to access from home to office, I can access the RDWeb logon page. After logon, I click the software icon, it shows the following

"The remote computer does not support RemoteApp. For assistant, contact your system administrator."

I forward TCP 443 and UDP 3391 to the server. Am I missing something?