When I had that problem I had to do a consistency check from the steam menu for the game, then it worked properly.
Right click Skyrim from the steam library, go to properties, then click the local files tab. From there, click the Verify Integrity of Game Cache and let it run (that is, if your game was dled from Steam. If not, don't know what to advise you on).
EDIT and Warning: Doing that may affect your installed mods, and you may need to reinstall your mods (if they weren't the cause of your issue) after doing that.
Right click Skyrim from the steam library, go to properties, then click the local files tab. From there, click the Verify Integrity of Game Cache and let it run (that is, if your game was dled from Steam. If not, don't know what to advise you on).
EDIT and Warning: Doing that may affect your installed mods, and you may need to reinstall your mods (if they weren't the cause of your issue) after doing that.