Exchange Outlook Calendar Disappeared from iPhone

Hi, I am running the most recent update for both iTunes and iPhone. I sync and update daily with iTunes. I have my work email on my iPhone it is an exchange emai and it is Outlook. For the past 18 months I have not had any trouble, however I noticed several days ago that my exchange outlook calendar is no longer on my iPhone. The settings shows that it is synced, I have chosen to dispaly my exchange calendar. I also deleted my account and re-entered my account -- and restarted my iPhone. However, my exchange calendar is still not on my iphone. Any suggestions or ideas? My work's IT department has been trying to troubleshoot this and has been helpful, but we are all out of ideas.

Thank you for your help!