Both kings cannot be in check, if it's whites turn then black must have made an illegal turn to not avoid check on their last turn.

The white pawn has advanced across the border but hasn't been promoted. A second white pawn moved backwards. Black has a pawn not promoted.

I guess technically white could have promoted a different pawn to be a third bishop, but white is not missing a pawn.

White king and queen could not have moved if the bishops and pawns hadn't (or the pawns would have had to walk backwards)...