The solution to Cydia not working, crashing or not opening is to rejailbreak by unc0ver jailbreak tool as long as you use unc0ver tool to jailbreak your devices before.
Why can this method fix the problem? Because using unc0ver to jailbreak has this situation, when you restart your devices, jailbroken status will become unjailbroken.
Sometimes the devices may restart on their own for some reasons when you are not aware of it. Therefore, you will be surprised while Cydia is not working or not opening.
How to fix Cydia not working, crashing or not opening?
Step 1: Open unc0ver jailbreak tool.
Step 2: Jailbreak your devices again.
Step 3: Wait for restarting your devices if jailbreaking completes
Step 4: Use Cydia.
How to fix unc0ver not working, crashing or not opening?
If your unc0ver jailbreak tool has the same issue as well when you use it to rejailbrak, please reinstall it from the site you download it to try again or follow this solution to fix unc0ver not working.
The high probability is due to certificates of your unc0ver jailbreak tool revoked. Becasue Apple requests that apps have Apple certificates and are able to be used on iOS devices, you need to get that unc0ver with working certificates or sign apps on your own.
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