Multiplayer works on single computer but will not work on multiple different computers.

I know this question has been asked before but I can't seem to find the right solution. I can get my multiplayer game to work on one computer but it will not work across two different computers. I have tried adding the Unet id in the player tab but to no avail. Does anyone know any other common solutions/troubleshoots in order to get this to work?

Thanks