In order to see whats going on you'll have to seperate the upper frame from the grip frame. this is done by driving out the 2 plastic 3/16th pins in the front and back. Then also remove the bottom mainspring cover and removing the mainspring tension. The the two come apart. Watch the trigger bar spring b/c they often come off the trigger bar and snap your finger and it just plain hurts. Go here http://shopruger.com/partsSelector-LC9.html
Number 11 is the magazine safety. Its a flat piece that slides forward when the mag is inserted. the safety engages a notch in the hammer to lock it when a mag is not present. Pushing a mag in forces the plate forward and out of the notch. You can see it up at the top of the mag well. Try pushing it forward with a screw driver and see if it releases. If it does then its not fully moving out and needs to be releaved on the inside cutout at the front.
The hardes part is getting them back together bc the hammer stop that is pinned in the grip frame is a bugger to get back into place. the key is to use a long small punch. Drop the upper down into the grip frame half way, from the rear push the hammer stop forward, push the upper down until it contacts the punch then slide the punch out and push the upper the rest of the way down. I've gotten good at it but it does take some practice. Just a warning, ruger will not cover it under warrenty if you send the gun to them in a bag
try a different mag if you can first. They are a simple design but takes a systematic approach to getting them back together.