This message is shown when Greenify detects its auto-hibernation service was not running normally or stopped unexpectedly. The most common cause is that the auto-hibernation mechanism of Greenify is being blocked by some 3rd-party system tool or system settings in some ROMs. You need to check those settings and explicitly allow (whitelist) Greenify to get it to work.
The specific settings varies from device to device. Some typical samples:
- [Sony] "Stamina Mode" in some Sony devices.
- [MIUI] Security - Permissions - Autostart.
- [Tool] AutoStart XXX / AutoRun XXX / Startup XXX / XXX Booster (various tools in this kind of name)