Anti theft not working after (simple) phone reboot

Please, help me trouble shoot this!

Phone: zenfone3, Android 6.01 marshmallow, install anti theft v.4.2.0.

App set as administrator with all permissions requested.

Setup a number of times, with our without stealth, cleared data, reinstalled. … with no luck-

app works as expected after installation, can access from Web, can send/receive commands etc.

The moment the phone is REBOOTED, make a note- not a factory reset, simple reboot. …

App no longer is responding to dialed PIN, if in stealth mode is dead (have to remove administration, uninstall) … if not in stealth mode - have to start it (!) manually to make it work? ??!

What’s going on? What could be making it not restart upon reboot? ???

I have no funny memory cleaners, no “power-saving” apps. … just the phone as it is. …

How do I trouble shoot and FIX this?
:cry: