unknown error code -24 I have Android 4.1.2 on Samsung galaxy S2

I install an app and get this error:

unknown error during appliaction install -24

googling this line should clearing Google play cache might help

but it didn't work for me. Any other solution?
I've just checked that again: "Error -24" in most cases is caused by a failed install/update. To solve it, uninstall the app from your device. After that, you should be able to install it again.