Jailbreaking your iOS 9 device with a non-working Cydia app is like jumping from an airplane without a parachute. You are pointless on what to do with your Jailbroken device. Though there are certain long routes to install different tweaks outside Cydia, but none of them are advisable.
There’s a strange error encountered by few users after they successfully Jailbroke their iOS 9 device and opened Cydia app. After Cydia prepared its file system and respring the device, re-launching the app gave an ever annoying error: “Failed to fetch http://apt.saurik.com/dists/ios/1240.10/main/binary-iphoneos-arm/Packages.bz2 Hash Sum mismatch.”
Solution is stranger than the error itself; we are clueless on how does this solution prove to be working, as there is no logical explanation associated with it. Just read the guide given below.
How to Fix “failed to fetch” Cydia Error on Jailbroken iPhone and iPad Running iOS 9
Step #1. Toggle OFF Wi-Fi from Settings → Wi-Fi.
Step #2. Toggle ON Cellular / Mobile data from Settings → Mobile → Mobile Data (Some users will have Cellular data instead of Mobile data).
Step #3. Now open Cydia app, tap on Sources located at bottom.
Step #4. Tap on Refresh option located in top-left corner.
Step #5. You will likely get the same error of “failed to fetch”, but without the long Hash Sum mismatch.
Step #6. Again tap on Sources tab in Cydia and tap the Refresh option. Cydia will reload the data successfully this time.
That is how this error is resolved; it seems strange that turning off Wi-Fi has anything to do with loading sources. One of the users has also commented that using iCleaner app solved this issue for him, but again how can we install iCleaner when Cydia itself is not working. Though there is a work around to install tweak outside Cydia, but it is a time consuming process and also not advisable.