Android device chooser - My device seems offline

Go to DDMS->Devices->Click on View Menu Down arrow on right side -> select "reset adb" option it will work

In Android Studio: open the Android Device Monitor (Tools->Android) and click on the arrow on the 'Devices' tab to reset the adb

I've seen this happen a few times on my HTC Desire. I've never figured out whether the problem is in adb or the device but I usually do the following:

• Restart adb by issuing 'adb kill-server' followed by 'adb start-server' at a cmd prompt
• Disable and re-enable USB debugging on the phone
• Rebooting the phone if it still doesn't work.

99% of my issues have been resolved with these steps.

I tried everything mutliple times in multiple orders, then stumbled across my particular answer:

Use a different USB cable - suddenly everything worked perfectly.

(Another potential answer for people that I found - make sure there is more than 15mb free space on the device.)