Hi, when I try to set the gateway IP for my APN to my 3G router it says: SIOCADDRT: No such process
What is going on? Is there a problem with my Linux install? Why doesn't it take my routing settings.

I had a look at your server, and yes, the routings are not set up.
However, I also notice that your server network address is 192.168.5.10, with a mask of 255.255.255.0, and that your gateway to your 3G is at 192.168.6.2
That is a problem, because you cannot set a gateway that is in another network than your local network. That is why it is giving you 'No such process'. It is because it is invalid to set a gateway IP that is not in your local subnet.
You should set your normal gateway for that network if it is not on your local subnet, and then from that gateway you must make sure it is set up to connect to your 3G router for the APN's IP range.