I have tried everything to connect my phone to my Ubuntu computer and nothing is working. I have tried 3 different phones (mostly Nexus 4) on MTP and PTP protocols. ADB Debugging is on as well as install from unknown sources. I have connected to adb one time but have never been able to since then. adb usb, adb tcpip both say device not found (all of these with phone plugged in). adb devices shows up empty. adb connect [IP] returns "unable to connect to [IP]" (I have adb over network enabled and it works on other computers). When I plug my phone in it doesn't even detect that its connected to a computer no matter what usb port I try.
What else can I try to connect it?
I figured out what the problem was. The cable I was using either has something wrong with it or is only for charging not data transfer. Whatever the case, switching to a different cable solved the problem.