Can't authorise android device in USB debugging mode I am trying to use a Samsung Galaxy S6 Edge for debugging an android app.
I've downloaded and installed the Samsung USB driver but when the device appears in android studio it says the device is unauthorised. 
I've got my phone connected in transfer image files mode (PTP mode). I've tried turning USB debugging on and off and after reading other forums it says I should get an authorise pc message on my phone but nothing appears.

Any idea how to get it working?
By deleting the adbkeys file found in C:\Users[Username].android folder the permission dialog appeared on my device.