If the gun is failing to latch when cocking is attempted it may be just an adjustment of the screw on the bottom of the trigger. Try backing it out (turn counter clockwise) one or two full turns and see if it will latch. Beyond that it may involve cleaning and / or lubrication of the trigger mechanism, which would necessitate disassembly of the gun.
OK had the rifle into the shop, if you look at the picture you will notice the scope stop has been removed from the rifle but the screw has been reinstalled, it is now protruding into the action and is stopping the slide plates in the trigger from moving, will some times cock and sometimes won't...if you remove the scope stop do not reinstall the screw...that simple