If your device has the iOS 10 Jailbreak there is a very annoying bug that doesn’t allow you to use your cellular data connectivity, iMessage app, or FaceTime app. This is a very simple fix, and before you begin make sure your Cydia app is launching properly.
Fix iOS 10 Jailbreak Bugs
Once you have Cydia open, search for MTerminal. Go ahead and install it on your device.
The next thing you’ll need to do is type in “OpenSSH” in Cydia and install it.
Once you have both of these installed on your device, go ahead and open up the Terminal application. Once you are in Terminal, login. You will be able to login by typing in “su” and hit return. The password is “alpine”.
Once you have entered the password, hit return. You will now have root access. The four commands that you will need to enter in the Terminal include:
chmod 777 /var
chmod 777 /var/mobile
chmod 777 /var/mobile/Library
chmod 777 /var/mobile/Library/Preferences
After you have entered all of the above listed commands, hit Return. Power off your device, re-enable your jailbreak, and you will be all set. Everything should be working for you if you followed all of the above listed steps exactly.