The bedding and/or the placement of the bottom metal is not in the correct position. When you bed the stock to the action, you have to make sure the magazine lines up correctly at the proper height for feeding. It sounds like the magazine is now in a position too low for the bolt to pick up the round from the magazine. The gun smith should have checked the feeding prior to delivering the rifle to you. It will have to be taken apart, and adjusted for fit. Usually that means a dremel tool and trial and error. The bottom metal needs to get higher to the bolt (remove bedding material under the bottom metal), so the mag sits higher to feed the round. It is a simple fix, just takes some tial and error to get it right.