This is your problem. localhost means the computer that you are on. If you want to access your DVR server from inside your network, you need use its IP address. (Or, if you've enabled Bonjour, using its name.)
On your DVR's web UI, on the Basic Setup section, you'll find the Bonjour option, which is enabled by default. Under that will be text, such as: Advertising dvr-channels.local. via 1 network: [10.0.0.81]. The name it is advertising is the host you can connect to—dvr-channels.local in my case—or you can use the IP address specified in brackets—10.0.0.81 in my example.
So, using my values, to access your DVR from inside your home, you would use:
-
http://dvr-channels.local:8089, or
http://10.0.081:8089
Hopefully this clears a few things up. (The hostname localhost, and the IP address 127.0.0.1, are what is referred to as the loopback interface. Regardless of the computer or the operating system, these will always refer to the computer you are using; they will never refer to other computers on your network.)