Trouble accessing TC from outside LAN

[DoFoT9]

hello all im having some trouble accessing my TC from outside my home network. i have set the connections up on the TC using provided guidelines from here and the internet, but cannot get into my TC when i put in my external IP.

i do have it behind a firewall router, and have allowed the afp port 548 on on the firewall. i was just wondering if there is any obvious things that i could be doing wrong? always worth asking,

thanks in advance

DoFoT9