Try this man:
1. Uninstall Appsync
2. Navigate to var/mobile/Library/Caches (with iFile or SSH)
3. Delete files: com.apple.mobile.installation.plist and com.apple.LaunchServices-045.csstore
4. Reboot device
5. Reinstall or Update evasi0n 6 untether & UIKit Tools from Cydia (reinstall or update packages, never uninstall)
6. Reboot again
7. Install Appsync from Cydia
8. Reboot
9. Done
10. Sync
Find UIKit Tools: On Cydia installed packages screen: Click the top right button "simple" to switch to advanced view... then find UIKit and reinstall it.
(found on google, idk exactly where)