USB Android Debbugging, I've tried everything I can think of
I had a problem with my LG Nexus 4 not being recognised when I connected it to my laptop and in the end this solved the problem for me...

On your mobile:


Go to Settings > Storage > USB Computer Condition (Menu option from Storage Screen)
Change from Media Device (MTP) to Camera (PTP)


After that it was recognised without any issues.