Can't connect Nexus 4 to adb: unauthorized

Question

I have a Nexus 4 with Android 4.3 and I am trying to connect the device to a computer with Windows 7 64bit.

I installed the latest drivers and the latest adb

Answer 1

For me once I disabled MTP (in Settings>Storage>Menu>MTP) I finally got the RSA prompt

Answer 2

Use a different USB cable. Some cables may not have all pins connected or whatnot, and while they work for image transfer, the debugging/adb does not work.

The bottom line: I kid you not. A cable which works for my phone (adb works) does NOT work for my tablet - the device is always offline or unauthorized and tablet pops out no dialog. I tried multiple reboots, settings, I went berserk in the process and cursed the bloody Android. Then accidentally I plugged in the cable which came with the tablet and suddenly it worked. My fascination with Android is definitely gone. What a stupid piece of junk.

Answer 3

I think it has an error when the device tries to display the screen asking for permission, so it does not appear.

This works for me (commands are given in the adb shell):

1. rm /data/misc/adb/adb_keys;
2. I sent the public key (adbkey.pub in ~/.android/) from my computer to my device via email;
3. Invoke stop adbd;
4. cat adbkey.pub >> /data/misc/adb/adb_keys (authorize myself);
5. start adbd (restart adb with new keys).

Answer 4

This kind of an old post and in most cases I think the answer that has been upvoted the most will work for people.

In Lollipop on a GPE HTC M8 I was still having problems. The below steps worked for me.

1. Go to Settings
2. Tap on Storage
3. Tap on 3 dots in the top right
4. Tap on USB Computer Connection
5. UNCHECK MTP
6. UNCHECK PTP
7. Back in your console, type adb devices

Now you should get the RSA popup on your phone.

Answer 5

I was able to solve this one by following the steps listed here:http://forum.xda-developers.com/showthread.php?t=2247471

delete the computers adb key: rm /data/misc/adb/adb_key on device 

(I have no idea if in case of multiple authorized computers the additional keys are in a new line of the file or if they are in new files. I have only 1 computer.)

stop all adb processes "killall adb" in linuxoids and "taskkill /IM adb.exe" in windows or simply the taskmanager in both.

restart the phone

toggle usb debugging off and on

connect

use adb

click authorize

Answer 6

If you are on adb over network, try to connect via USB instead or vice versa. This did the trick for me. After accepting it once it always works later on.