Suggest reading this article first : Jailbreak 9.3 Complete Guide
Apple Remove This App Certificate, However the app owners are working on a new certifitcate .
Steps to follow :
1- From your your idevice visit this website : jailbreakme9.com
2- Tap on "Download now" . If it doesn't work, click here for the computer method.
3- Trust the app, from your idevice go to Settings > General > Device Management. then trust the app.
Launch the PP app and ACCEPT NOTIFICATIONS
Next, tap on the circle in the app, and then it will turn into a line of text.
while your device is locked, a notifcation will appear on your locked screen, open it and wait for your device to reboot.
Enjoy Jailbreak :)