Steam Multiplayer isn't working. Tried everything

Hey there!

I am trying to implement multiplayer into a small learning project/game project. So my problem right now is that when I create a LAN match, I can find it in my server list, but when I create a public/Steam match, my friend cannot find the server on the server list. I searched everywhere online and tried the methods that I saw, but non of it worked. Here are some questions people might ask:

What are your packaging settings?

My settings are like this for Packaging:

Steam Integration does not work when packaging a shipping build, I would have to add the game to Steam and create a steam_appid.txt with the id 480 inside of the main game folder. Playing in standalone mode has steam integration working (i mean shift + tab works.)

How did you test it out?
I packaged the game like mentioned in the text and sent it to my friend in a zip file. He added the game to Steam and I hosted a game. He couldn’t find it in the server list. LAN works fine in the shipping build too. Here is my Build.cs and Target.cs if this helps:

That’s all I have. I’d appreciate any response. Tried everything, I have no idea what to do now.