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USB Keyboard Plugged into Monitor Often Doesn't Work

Very often the USB keyboard plugged into the 27" Thuderbolt Display will not be recognized. It can be worked around by plugging the USB keyboard cable directly into MacBook Pro (which always works) but the whole point is to leave the office desktop peripherals connected to the monitor when the laptop is taken away. The keyboard is a new Apple full size USB US keyboard with integral numeric pad.


17" MacBook Pro late 2011, Lion (now 10.7.3) always up to date with all Apple software and Firmware, including all the Thunderbolt Firmware updates. The problem has been occuring since 10.7.1 or 10.7.2 (sorry, can't remember exactly what we started with but it definitely predates 10.7.3).


A temporary fix can be achieved by performing an SMC reset but the problem recurs afterwards episodically upon a subsequent instance of the computer being detached from the monitor and then reconnected.


Attachment/detachment (computer to monitor) can be either while machine is off, on, or asleep and the behaviour is the same.


Everything, all powered devices, are conencted to a new UPS with AVR and active power factor correction CyberPower CP1500PFCLCD and no events are being logged (that is, logging is active but nothing has occurred).


Thoughts, suggestions, other data about set up that I ought include?


Thanks in advance for any enlightenment.

Thunderbolt 27" Display-OTHER, Mac OS X (10.7.3)

Posted on Feb 14, 2012 4:33 AM

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Question marked as Top-ranking reply

Posted on Jun 17, 2017 11:03 PM

I share a workstation with my partner, he has no issues with the keyboard, but I was going to buy a new bluetooth one just for me, because it was really frustrating.



My fix: while everything is plugged in, in place and on, unplug the cinema display from the power outlet, & plug back in.


so far this is the only consistent fix for me

116 replies

Jun 19, 2017 6:03 PM in response to Prag mac´ tic

I see the same problem on the MacBook Pro 2016 (USB C) with the LG 24" USB C display and Apple USB keyboard and wired mouse. I'm using a USB-A to USB-C adapter cable with the keyboard which is not sufficient to resolve the problem. Unplugging the cable on the back of the monitor and plugging it back in always works to get the keyboard/mouse recognized.

USB Keyboard Plugged into Monitor Often Doesn't Work

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