Welcome back Matko!
I am not very tech savy, so not sure what your problem could be, except maybe what Tree said. If you just downloaded the nxt client, it needs to download the game data into cache or something like that. When you launch it there should be a small spinning circle on bottom right, with a % number. Let that run to 100% (or until it is gone), then the whole game data should be downloaded.
You would only have to do it once (unless you delete everything again and reinstall, then you should do that again). I am not sure if you actually have to be in lobby for it... I would think it would work from login screen too.
Hope that helps!
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