why my phone doesn't let me enable mock location?

[xXxProTixXx]

when i am trying to enable mock locations on my LG G 3 its reset to default automatically and disable the mock locations. if some one know why i will be very happy if will tell me.

 

[mhinc]

when i am trying to enable mock locations on my LG G 3 its reset to default automatically and disable the mock locations. if some one know why i will be very happy if will tell me.

Are you the admin or on another profile? Do you have developer enabled? You have to choose the mock app from there.
Oh and if you are doing this to try and trick Pokemon Go. It doesn't work