yeah so I keep getting a port 6112 is blocked error and I can't figure out the cause.
My fw and router both have rules to allow the port.
I still get the error with both my fw and mse turned off / directly in modem
I reinstalled d2 and delete bnetcache
I can connect perfectly fine in a sandbox but I still can't connect regularly

...any ideas...

^^

did you go run--->cmd---> ipconfig /all and see your IPv4 Address? It would say (Preferred) You'd use that as the IP when forwarding port 6112 in your router config (192.168.1.1). It can change frequently so always check you're using the right ip (last 3 digits usually change)