For the non closing bolt, there's a chance that your bolt head has unscrewed by one complete turn. Correct this problem first. If the cartyridges won't load from the magazine it will only be one problem with a couple of causes. The problem is that they're not high up enough in the magazine well - caused by a defective magazine or that it's not positioned in the magazine well correctly.

If it was all working correctly before, then it's clearly something that you've done since