Jenkins : Jenkins jobs not running as per scheduled time.

Jenkins jobs are not following the 'build periodically' feature enabled in the configuration page and none of the jobs are triggering as per the scheduled time. Our jenkins instance is hosted on a server located in US/CDT timezone and we were clueless about the root cause of this issue.
We restarted the Jenkins Master multiple times and checked all the hardware configurations and it seems all ok but unable to find the real cause of this issue. Appreciate if someone could shed some light on it and share their suggestions.