If it is Pangu Jailbreak you have jailbreaked with you have to open the app on mobile and re-jailbreak it. If you jailbreaked in on PC you have to connect your iDevice, open up Pangu and click a button i dont remmenes right now.
It's all because the jailbreaks theese days is under untethered - and thats mean every time you shut down or the battery is drained and shut down, you have to "re-jailbreak" it.
I had the same issue almost a year ago.. I hope it will fix your problem, if not, you're welcome to PM me anytime. I know pretty much about jailbreaking, the issues and more...
Regards
Martinooo
EDIT: It sounds like your jailbreak has failed. Are you doing it on a PC or by the iDevice version?