Cooper hasn't played much and dropped the one chance he did get.
We knew this was the offense's weakness going in (especially without a lot of Cooper) and they aren't running well enough to make up for it against a really good pass defense.
IMO that's coaching and scheme. Look no further than the team they are playing today. The Titans have a worse QB and their WRs aren't much better than the Bills but they don't have issues competing passes and moving the ball.
The Bills for some reason rarely take deep shots. They stay with the short passing game and its not working.
The game they took multiple deep shots Allen went 9-30. They don't have the personnel. Tennessee established the run, that's what opened up the middle in the passing game.
The Bills need to be able to run to set up the pass with this roster.