Android Studio 2.1.1: "no usb devices or running emulators detected"

Question

Suddenly my Android Studio stopped detecting all my devices, none of them is working. It happen from one execution to another. I've changed a few lines of code (1 min maybe?), hit run (instant run) and then I missed all my devices.

I'm using a Mac and as devices: Nexus 5x, Galaxy s6 and Oneplus One. What can be happening? I've checked previous questions here and tried all this:

• Run configurations: no matter if I chose usb device or show the window, it does not work.
• Tools > Android > Enable ADB integration: didn't help
• Command line adb devices does not detect any either.
• I've revoked and granted again USB authorizations. Still not working.
• I've tried other apps I have, none work.
• Restarted phones
• Restarted android studio
• Restarted computer

(Note: if I start an emulator it works, but I'd prefer to use physical device since I have to scan real barcodes)

Thanks a lot in advance.

Answer 1

On Lollipop 5.1

1. Go to About Phone
2. Click 7 times on Build Number. Now Developer options are enabled
3. Go back and Click Developer options
4. Enable USB debugging under Debugging.

Answer 2

Well, I've fixed. The problem in case any faces the same was a Stetho (http://facebook.github.io/stetho/) tab in chrome, the one you open by typing: chrome://inspect/#devices not sure about the reason because it's been open for 2 days now, but it was the cause, once I closed it, it worked.

Found this unaccepted answer here: macbook adb cannot open interface That for sure should be accepted.

EDIT: I've been able to replicate the problem. It happens when you have the devices tab open and try to run a second app that has stetho configured.