You may have an update waiting, or you may have to restart your chromebook; I myself am using a school chromebook from my college and that seemed to fix the issue (restarting it, I mean.). I think it has to do with when you close the chromebook it goes to sleep and doesnt turn off, so after awhile the small automated updates that come out once or twice a month (maybe more) don't get installed automatically like it would on a regular PC.