The "app not installed" error will happen if you are trying to override a stock app with a themed/inverted app w/o uninstalling... the signature key we use with apk manager doesn't match the key the dev used so it will not replace the app.. if you uninstall and THEN install a themed /inverted app then it works and any updates we do or another themed version of that app from the forums it will replace w/o having to uninstall first.. that's for data apps...now for system apps that either come with the rom or gapps or you'very pushed to system .. anytime you edit a system/app you MUST reboot for the changes to take affect... and I recommend uninstalling the app rather than just deleting it.. after rebooting you should be able to install it just fine... signed apks usually install to data even if its a system app so you do need to verify its where-abouts and move it appropriately.
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