I had this problem, it turned out that the Performance Analyst who had been assigned to scouting next opposition had left the club. I went to Staff>Responsibilities>Scouting and under "Providing Opposition Analysis Reports" I set a Performance Analyst who didn't have an assignment already (when my Performance Analyst left the game defaulted to my Head Performance Analyst, but since he already had another assignment I guess he was too busy to provide the reports!).
Hope this works for you too!