1. So you have a Horizon View Connection broker?
2. You can connect with the Horizon View client from internal network?
3. You can not connect with the Horizon View client from the external network?
If the answer to 1,2 and 3 is yes then you have either not configured your external URL and PCoIP gatweway IP correctly or a firewall is blocking the traffic on the way in or out.
// Linjo