"Session Disconnected" timeout using WAN connection - but not over LAN

I am using PocketCloud on an Android Galaxy S II device with Windows 7 Ultimate. When at home using my local LAN/WIFI connection (192.168.x.x) connection, I can set the phone down and come back several minutes later and continue in my active session.
However, when I connect remotely through a WAN connection (via phone data/Hotspot), if the phone is left inactive for a minute or two and I tap on the screen I will get a "Session Disconnected" message and have to log in again.
Is there a setting in Windows 7 that I can/need to adjust to prevent the disconnect over WAN? There are no "timeout" settings specific to PocketCloud that I have seen.

Thanks