What was found
AIRCRAFT WAS GROUNDED: FIRST OFFICER'S SLIDING WINDOW IS STUCK IN THE CLOSED POSITION AND WILL NOT OPEN. MAINTENANCE EVALUATED THE SLIDING WINDOW AND FOUND OPERATING HANDLE RELEASE PUSH BUTTON JAMMED, EXTREMELY DIFFICULT TO PUSH DOWN TO RELEASE LOCKING MECHANISM TO OPEN WINDOW. MAINTENANCE LUBRICATED THE SLIDING WINDOW ACTUATING MECHANISM AND HANDLE PER AMM 56-12-12-0401. A SATISFACTORY OPERATIONAL CHECK WAS ACCOMPLISHED.