Default Settings - verify applications - inactive - SOLVED

Installing plenty apps of different sort I noticed that I have no longer option to enable/disable verifying of applications I want to install (below checkbox "unknown sources".
I have System Tuner, DroidWall, Xposed modules, BetterBatteryStats, more ...

I wonder how can I discover which one made verification switching impossible.
I'd prefer not to uninstall one after one.

Any hints ?

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I found reason.
Verifying process was disabled by me in Google Play Store.

Case closed.