If you cannot access a game with the invite link, you can try join using the room name (same as the hosts's username) and the room password the host used when they created the room.
If you are a host, send those values directly to your friends. If you're not the host, request those values from the host.
After logging in to the game, click "Join Game" and enter the values into the dialog.
Please note: The host needs to be in the room before guests can join.