why usb thethering option is blank. its not clicking pls solve this my problem

[AC Question]

i connected usb cable mobile and computer. but there mobile thethring option is didnt click. its like not a option on phone. but there is present. this coloured in grey or black colour.
eg bluetooth tethring is clinking but usb thethering not clicking

 

[anon(632115)]

Have you installed the drivers on the PC? What phone is it?