Big Sur - will not boot with Thunderbolt monitor connected

When you press the Reply button to leave a reply the form that opens up says "Tell us what's on your mind". When I saw that appear I felt reassured that Apple cared about me and my problem (Big Sur won't boot up if my Thunderbolt is connected to my MacBook Pro 2013 Retina). But then I remembered reading the comment from someone else with the same problem I have. He reminded us that Apple's own Technical Support people do not have access to these 49 identical problem reports others posted here who made the same mistake I did by installing Big Sur.

Does anyone know who the smart *** is that came up with the "Tell us what's on your mind" message that greeted me just now? I would really love to take him or her up on their offer and TELL THEM WHATS ON MY MIND. I promise when I'm done he/she will be sure to tell Technical Support to issue a warning to everyone with a Thunderbolt that Big Sur isn't so big after all.

Escribe Del Fuego

This is same happened to my Macbook Air 2014.

My Thunderbolt Display is attached to Macbook Air all the time this while. After upgrading to Big Sur, it cannot restart properly- It just turned to blank dark screen, the machine not responding at all.

I have to unplug my Thunderbolt Display and other USB peripherals that attached on my Macbook Air to perform restarts.

Similiar issue, I have a 2017 Macbook Pro with a older 27" Mac monitor connected via Thunderbolt adadpter. I installed Big Sur and it worked correctly for a few days. Today, I cannot detect or use the external monitor. I tested another laptop that has not been upgraded to Big Sur, plugged it in and it worked perfectly.

Solved! I installed todays new update (catalina 10.5.7) on MBP Retina 2014. Now Thunderbolt Display works normal and boot with connected Thunderbolt Display is possible.

Thanks to the Apple dev team.

But when big sur breaks your thunderbolt it remains broken if you roll back to Catalina because it’s the firmware not the software version that broke it.

ergo when updating to Catalina 10.5.7 fixed firmware is installed which does fix the problem and is therefore fully relevant for this post.

The thread big sur will not boot with thunderbolt connected is incomplete - it should be MacBook will not boot with thunderbolt connected. Big sur breaks the firmware which is the same firmware used if you roll back to Catalina.

i find it hard to believe they gave Catalina a new firmware that works but apparently doesn’t on big sur, perhaps additional steps are required if you haven’t done them like resetting the smc and pram?

Back in November I had upgraded to Big Sur (Mac OS version 11.0) from Catalina. Upon upgrading, when my Thunderbolt Display was plugged in the OS would not boot. I reported this to Apple (and here on this board). Apple ran diagnostics and told me that this was an unexpected side effect of the upgrade process (I believe a firmware modification) and that on upgrade to the next patch - they expected to have this fixed.

I checked the 11.1 release notes and it is not listed. But assuming that what the development team told me - this is not unexpected. As it was a pretty widely reported but non-critical issue (which is why they did not expect to release a special patch just for the monitor issue).

Last night I upgraded to Big Sur 11.1 - and the issue is now fixed! Here is what I did ...

First I started the upgrade with everything plugged in (that means the Thunderbolt Display and my other peripherals - which attach thru it and my other thunderbolt hub, a Legato port replicator). After the first boot - the machine hung up just like it has before whenever the Thunderbolt display was plugged in. I expected this to happen because the first boot is really nothing but a reboot after the download to initiate the upgrade.

So after I manually hard powered down the MacBook Pro by holding the power button - I restarted the boot process. Upon seeing the first Apple symbol on the screen (now of the MacBook's built-in display) I plugged the Thunderbolt Display into the machine.

The upgraded proceeded as normal. It rebooted several times, I want to add, without issue. The process ended late in the evening and I came back to the machine this morning. I reconfigured all the physical connections by removing everything from all the ports, booting the machine without any displays (I also have an HDMI display attached) and any other peripherals. Then rebooted. And finally put everything back together again ... and did one final reboot.

As of right now ... everything is working and the machine appears to boot correctly.

I believe, that the upgrade migrated the firmware back to a point where the Thunderbolt Display can now be booted. And that by plugging the monitor in at the beginning of the upgrade process the upgrade did that. My guess is that anyone that has downgraded back to Catalina, might be able to fix their boot up issues with the display by also upgrading to Big Sur 11. If they want to remain at Catalina; they could downgrade again -- that though would be a pretty painful process as it would like take 3-4 hours running a 6+ year old MacBook like mine.

Good luck to everyone ... it sounds like Apple has done what they said they would do. If you still cannot get your display to boot up properly I would suggest contacting Apple Support and having them analyze your specific issue. It might be something different than what I and some others have reported.

Sorry but Yes it did fix the issue 100% as I am now typing this on the Thunderbolt Monitor I have been unable to use for weeks.

You only have to read the number of posts here with people saying it fixes the issue to realise it fixes the issue.

And saying "it wasn't released to do that" could equally apply to Big Sur 11.0 which wasn't released to break it in the first place ;-)

The release notes for Big Sur 11.1 are for the OS not the firmware. You would need to see the EFI firmware release notes to know what hardware incompatibilities have been resolved.

I feel your pain I bought a £45 Apple thunderbolt 3 to Thunderbolt 2 adaptor so I could at least use the monitor on my Windows laptop which has a USB-C with thunderbolt port............yep that was a waste of money laptop sees the port but wont authorise access to the monitor.

Have you tried Apple support using chat, they were brilliant helping me out up to the point when it became obvious it was a problem with the firmware?

Hi Andy - yes thanks did that, it is known firmware issue. I have a workaround, I bought a cheapish video conferencing camera and attached it via third party USB hub on the MBP then clipped it over non-working camera on thunderbolt screen. It's a bit clunky looks silly, but sort of works in that I can see all participants clearly on work calls.

See also this thread... It's the same story.

https://discussions.apple.com/thread/252038098

Same here. MacBook Pro (Retina, 15-inch, Late 2013). 27" Thunderbolt monitor. Does not work. If you book without the monitor, all is well, then plug the monitor in.

I have the same exact issue :(

i wish I didnt upgrade my mac.

2013

15 inch

I have the same MacBook with same problem, I have to unplug my Thunderbolt Display boot-up then plug in the display. Keeping checking for a Software Update hoping they address the problem.

GeoChester, I would expect any firmware update will fix both Big Sur and Catalina issues. It is my understand that firmware changes how the hardware reacts with the software.

Paul