Cannot access CCTV cameras away from home

I have a Yale Smart Home CCTV Kit XL (SV-8C-4ABFX) which is ONLY good for home viewing; I can never view any of the camera feeds when I am away from home (and it is directly connected to a 100Mb fibre internet line). I have complained several times to Yale Sa, and was told to reset the DVR internally, plus delete the system from the Yale App and reload again. However, nothing works! I would never recommend anyone buying this system