I have an RB750UP setup, and I have a DVR system connected to it. I can access the DVR system locally at 192.168.88.199:8080

I want to access this DVR via the internet, so, pretent my WAN IP is 50.50.50.50
I created a rule to allow me to access port :8080 via my WAN IP address, and forward it to that port.

When I type in the address in my web browser for example, http://50.50.50.50:8080/ The page does not load, but, it does load the title of the page, as if it is almost working.
Do I need more rules to allow this to work?

Make sure your DVR has the gateway IP set. If it doesn't, it will work on LAN but not from Internet.