"Unable to connect to server"

[igloooooooo]

I am trying to play a multiplayer game with my friend, but when she tries to connect to my server, a small dialogue box saying "Unable to connect to server" appears. (See screenshot).

She is able to connect to other servers, so we're not sure why this isn't working.

We're on the same network, so it shouldn't matter, but I did set up port forwarding and it is successfully open according to http://www.canyouseeme.org/ 

[cascadia]

I don't have an answer to your issues, but I do want to thank you for troubleshooting yourself what you could before asking for help.  Too many people don't do that.