To make sure we are on the same page: did you try DHCP at office? If not, is it because your office network does not offer DHCP? The arrow displayed on the LCD means the controller is trying to reach the gateway. If it takes more than half a second, that means it can’t reach the gateway. So the first thing to check is whether the gateway IP is indeed correct. If you’ve used DHCP, you shouldn’t need to bother with it since the gateway IP would be automatically obtained through DHCP.