Can't create game. Firefox 61.0.2 (64-bit)
I cannot create a game either. Chrome 68.0.3440
it seems to be an issue with the cookies/cached data
There was a major update on the Lichess site a few days ago.
If you have cookies stored in your browser from before the update you might not be able to creae new games.
Delete the cookies\browsing data and it will work again.
It did for me.
It didn't work for me but it works now:)