if you tried to modify something in the files, you probably messed up the (zip) archive settings
Discussed many times - use old winrar, totalcommander or doublecommander

Or maybe you added a some bad file to your package or it's corrupted
There can be many reasons. You should start from the basics - a clean package and add only the necessary, verified, compatible files.
Also check that the settings in the sys file do not overlap with any other package in your device