mmmm sounds like you havent port forwarded in the main router on your internet, what router make have you got. and do you have access to the router login via a network cable?
Its a Sky Hub and I eventually managed to get it working on my home wifi and on the mobile network when away from home.
As you mentioned I forwarded the DVR's *mobile port number* and also the *HTTP port number* and associated them both with my DVR IP address within the router settings.
I then entered the relevant settings in the Android Mobile Apps..
I used Meye app for my home wifi network and VMeye for use with the mobile network when away from home.
I found this video really useful...
I hope posting this link doesn't break any rules
Thanks again for replies