Apps will not launch after Jailbreak with Pangu. Device is iPhone 4 running IOS 7.1.2

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Just jailbroken my iphone 4, evrything went well, Cydia loaded properly, rebooted a few times and now ready to go. But when I tried to install my apps, it installed but it's "Greyed" out and when I tapped to launch it will again try to install the app but nothing else happen. I can not use any of the apps that I was able to use when I'm on IOS 6. Anyone has similar problem? Please help!!