Freddy Eastwood scored the only goal, turning the ball home from close range after five minutes when Will Atkinson made the most of a defensive slip to tee the striker up.
Cooper suffered a second defeat without scoring in as many League Two games following an opening-weekend humbling at Rochdale.
His side dominated possession, but were unable to turn their advantage into goals. "As someone new into this job, I'll have to learn off frustration," he admitted.
"For the majority of the game the lads did what we are working on.
"We need a solution to putting the ball in the goal and we will do that. The bits in between are coming and the rest will be there.
"I cannot ask any more in terms of application and effort and all that.
"Balls in the box we did a lot and put balls into dangerous areas, we need the solution to scoring."