I've linked this phone to the same PC many times, but since upgrading to lollipop (5.0.2), my phone is not recognized (in adb devices) when I connect.
When I look in "Developer Options", "USB Debugging" is ungrayed when I'm not connected to my PC, and I can toggle it, but when I connect to the PC, it changes to gray. It changes to gray whether it was enabled or not before connecting.
If I choose MTP as my connect type, I do see my phone's file system from my PC, but there's still no "USB Debugging" link.
Trying to follow the directions on http://developer.android.com/tools/extras/oem-usb.html to connect a driver to this device, when the phone is connected, I don't see "Other Devices" in the list under "Device Manager".
My PC is running Windows 7. My carrier (who pushed the upgrade to lollipop) is T-Mobile.
I've already tried: - updating all the software in SDK manager. - installing a driver from the phone's "pc software". - downloading and installing a driver.
This also fails in the same way from one other PC we have at our company that is used to set up very many other phones.