Unable to activate Doorbell 2 remotely

Hi there, I have a Ring Doorbell v2. It is working fine except when I am away from the house I have trouble waking it up (activating it). It can push motion and call notifications to my phone ok but I have trouble connecting live. When I am home on my wifi it works fine. It is close to the wifi router and has good signal. The wifi router is connected to another router by LAN cable and then to the cable modem. I suspect it is a port/permissions issue. Do I need to change the port settings on the routers and/or modem?