Cant get system management (processes) on remote office PC's

I can click "manage" on PC's in the LAN (relative to the DC-server) and the local PCs will show processes, but when I connect to a remote PC it says unavailable every time.

" Your System Manager session has been disconnected because the agent is not reachable"

1/ Am I missing a setting for managing this remote PC?
2/ Where can I see the Ping distance (as measured in ms) for diagnostic purposes

I can remote-access the remote PC using the HTML5 viewer...
WAN ports forwarded to DC server:

8443 tcp

8444 tcp

8031 tcp

8032 tcp

8081 tcp

8082 tcp

8020 tcp

8027 tcp

8383 tcp