USB debugging option greyed out in Samsung Galaxy J5 runing Android 5.1.1 As per the rule with a new Android, I have tapped build number 7 times for enabling Developer option. However, USB debugging is shown as greyed out and I cannot start it. Samsung Galaxy J5 comes with latest Android 5.1.1. I have also updated the software to latest version.

Can anyone suggest me what to do?

Here is a screenshot:

(Click image to enlarge)
OK, here is I got the solution! there wasn't any bug or error in Android. It is because I have installed Samsung My Knox in my phone. Knox give an extra protection to device and also for some security reasons, Knox disabled USB debugging. 

according to Samsung My Knox :


  If you are using My KNOX, you cannot enable USB debugging mode while the container is installed.


I have uninstalled Knox and now  USB debugging is working properly!

There is another application named Samsung Knox Express which give you option for enabling USB debugging, but only System Administrator can install this application.