Lock applications on Tecno camon 16 premier

Hi,
The tool native "Lock application" on my tecno camon 16 is not working fine. When I open the tool and that I press an application to lock it and then I move back to home screen my lock action is immediately removed as if I haven't done it. When I try to use external tools like "AppLock" it works just the first times I've done the config. first open on the locked apps request the PIN or PASS or Schema. But after that it stops to request these on the second, third, etc attempt to open the locked appl. CAn someone help to fix