Visual Studio and Android Device Monitor doesn't detect any devices

I've just installed VS2015 Community with Xamarin to develop some mobile apps. The problem is, I can't achieve debugging Android apps on any device. Android Device Monitor shows empty list. I tried connecting different phones, which I know are detected on my friend's PC. I can explore their files from windows explorer, from there computer sees them.

• USB Debugging on the phone is turned on.
• USB connection mode is set to camera, no change at all.
• I have Google USB driver installed in Android SDK manager.
• I tried adb kill-server, adb start-server. Nothing changed. adb devices shows empty list.

This is device manager while Developers options are disabled on the phone. And here with enabled Developers options I also tried updateing driver to google usb driver, but windows said it's up to date.

You most likely did not grant access to the device. Try to go into the developer settings on the smartphone and revoke the USB debugging authorisation. Then connect the phone to the pc and and wait for a popup on the phone which you should accept. After accepting you should see your device with adb devices.

You can also try to set the connection mode to MTP (instead of the camera PTP).

Hope it helps!