"Air Video Server" and connecting to my router/Mac remotely.

[#1]

Hello all,
I'm looking for some advice. 
My current set up is a Thomson 585 v7 router, wifi switched off. It is connected to an Airport Extreme which is in bridge mode. I use a MacBook. 
For the past year I have been using a great programme call "air video server", which allows me to access my MacBook from my iPhone over the Internet. It set itself up automatically and worked a treat. 
A few days ago I lost internet connectivity in my home. I switched off my router, airport express etc overnight. When I turned it all back on the next morning plusnet ran an automatic set up on my router. Internet was back up and running. Everything worked fine, except the air video server. I uninstalled and reinstalled the programme but it still would not allow me to connect with my MacBook remotely. 
Is there a firewall issue? Has a port been blocked that was previously open? I'm using these terms without really understanding what I'm talking about  :). 
Any thoughts would be much appreciated. "Air Video Server" thinks there is a possible "double NAT" issue but as my Airport Extreme is in bridge mode I would have thought that wasn't likely. 
If you have made it to the end of this long winded post, well done and thanks for reading. 

[#2]

I'm not sure to be honest. If you haven't set anything specifically originally. In Toolbox>Game and application sharing make sure UPnP is enabled.

[#3]

Sounds like your router has been factory reset and so it will have lost the port forwarding rules, both Air Video Server and VNC need a specific port forwarded (usually 5900 for VNC and 45631 for Air Video Server) rather than uPNP as the connection is established into the home connection. You'll need to set these rules up again for the respective services to work.

[#4]

Thanks guys. I'll get into the router tonight and have a look.
I was lucky that Air Video set it up for me automatically last time, just a bit strange it won't do it this time.
This will be a learning curve if nothing else.
Thanks again.

[#5]

Thank you Ben.
I have solved my problem and learned something at the same time. Woo hoo.
Cheers again.