I have the DLINK DIR-882 and when I attempt to port forward 30120, it doesn't allow me to connect to my FiveM server. I use this tool: https://www.yougetsignal.com/tools/open-ports/ and I put my public IP address and the port and it says the port is not open. Any thoughts on why this isn't working?
If the IP assigned to the wan port does not match the IP you see on a site like whatsmyip then port forwarding will never work. The ISP has a NAT router between you and the internet and you would have to place port forwarding rules there which is not possible.