Upgraded to Sierra, External Monitor Stopped Working

Discussion in 'macOS Sierra (10.12)' started by Melrose, Oct 13, 2016.

  1. Melrose, Oct 13, 2016
    Last edited: Oct 13, 2016

    Melrose Suspended


    Dec 12, 2007
    I upgraded my 2015 top-of-the-line 13" MacBook Air to 10.12 yesterday, and after powering on this morning the external display won't get a signal. It worked after the upgrade yesterday - during which is rebooted and all that jazz it usually does during an upgrade. It's an HP 22cwa.

    But today, I fired it up and the external monitor is dead. It's 720p, nothing fancy, and never had any issues before.

    It's powered through a Thunderbolt-to-HDMI cable that's worked like a breeze until now.

    Any ideas or troubleshooting? Thank you in advance!

    EDIT: Maybe it's related to the fact that the Desktop Pref Pane wasn't loading until it rebooted? I dunno...
  2. sniffs macrumors regular


    Jan 24, 2013
    Did you install any of the 10.12.1 Beta 1 through Beta 3's? There are known bugs with those first 3 Beta's and external monitors. Beta 4 fixes it.

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