Can't join friend's lobby

Recently I’ve had issues with joining a lobby hosted by a friend (am doing this through Steam invites and joining using the “Join Game/Lobby” in the Steam Friend’s List).
I’ve tried restarting the game, turning relays on/off, switching to LAN, saving, then going back online. None of it has worked. I get the “Joining player…” dialog box in the bottom right of my screen, it seems to load for a while then gives me a “Failed to connect to lobby”/similar message.
Yesterday, I was able to successfully join my friend’s lobby, but only after many, many tries.
My internet connection was stable while attempting to join, as was my friend’s (have tried this with multiple people).

Anyone know a fix or solution to this? Or is this just a connection issue on my part?

Have the same issue here. Tried every solution google had thrown at me, and yet join attempts fail. And no, my internet connection isn’t a bad one. To support that I tried a different ISP and still no progress.

Let’s stick to recent threads.