Advanced Session lobby findable but can't join

[nande]

in my case the issue was that the map was not cooked properly so i had to add it to the list of maps to cook.

there are multiple ways to do so

List of Maps to cook

DefaultGame.ini [/Script/UnrealEd.ProjectPackagingSettings] bCookAll: if true, cook everything in the content directory. This means that if you have an asset that is not referenced by any others, it will still end up in the cook. From this it follows that the list of maps to be cooked is simply all of them, even if they are not in any other .inis. bCookMapsOnly: this setting only has any effect if bCookAll is set. If it is true, “cook all” does not actually cook every asset, just all maps and…

https://www.reddit.com/r/unrealengine/comments/6dq3ke/tip_if_your_packaging_games_with_multiple_maps/