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iMac Pro External Monitor not working after Security update 2020-02 & Safari 13.1 update(MacOS 10.13.6)

After doing a routine security update(2020-02) and updating to Safari 13.1, my external monitor(ViewSonic VP2768-4K) stopped working.


  • Rebooted. Did not fix
  • Full shutdown and turn back on, log in. Did not fix.
  • Open System Preferences. 2nd monitor not detected there. Selected "detect monitors" Did not fix.
  • Safe Reboot. Did not fix.
  • Unplugged the Display Port to USB-C cable and re-plugged on both ends, just to be sure the cable was properly seated. Did not fix.
  • Checked external monitor on MacBook Pro, to be sure monitor is OK. Monitor checks out OK.
  • Create new user account, and test. Did not fix.
  • Shut down computer. Swap USB-C ports on the back iMac Pro. Plugged the monitor into the port that had my external fiber channel storage, and plugged monitor into the port that was my fiber channel storage. External monitor is now working again after the power up. However, I cannot mount my Fibre Channel storage, which tells me I have lost USB-C port #4(the port sitting right next to the Ethernet connector), after the upgrade.



iMac Pro, macOS 10.13

Posted on Apr 6, 2020 9:17 AM

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Question marked as Top-ranking reply

Posted on Apr 6, 2020 12:09 PM

try zapping the pram.


SMC reset      https://support.apple.com/en-us/HT201295




Zap pram   https://support.apple.com/en-us/HT204063

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iMac Pro External Monitor not working after Security update 2020-02 & Safari 13.1 update(MacOS 10.13.6)

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