I'm just posting it here because I have another 39 minutes to wait for the lfg invite...
And I know posting it here won't change anything, but perhaps I get some comfort by telling.
So...I just had the lfg invite (after waiting said 39 minutes), I clicked Enter Dungeon - all 5 roles checked green, but nothing happens. After 30s, my symbol went red, and "you have been removed from the Dungeon queue because you did not accept the invitation".