macOS sequoia 15.2 update Mac Pro 2019 failed

Thanks @RoaringRatFilms! After turning off my Thunderbay enclosures my 2019 Mac Pro booted successfully. Then, after booting, I turn the Thunderbay enclosures on and all my drives mount. Only downside is that I must turn off my Thunderbay enclosures every time I reboot or turn off my Mac Pro but, for now, it works. I hope Apple is listening and will fix this in macOS 15.2.1.

Thanks to @RoaringRatFilms! post in this forum, I found the following workaround:

After turning off my Thunderbay enclosures my 2019 Mac Pro booted successfully. Then, after booting, I turn the Thunderbay enclosures on and all my drives mount. Only downside is that I must turn off my Thunderbay enclosures every time I reboot or turn off my Mac Pro but, for now, it works.

Hope this helps!I. And . . . I hope Apple is listening and will fix this in macOS 15.2.1.

Same problem here on my MacPro 2019.

After the update to 15.2 I was greeted with the black screen with the circle.

Now, the boot process hangs every time unless I disconnect all thundertbolt 3 devices. I have tried OWA Thunderbay 4 and OWA Thunderbay 4 mini. After booting has finished, I can reliably reconnect the devices and they will work.

Older thunderbolt 2 devices seem unaffected. I have tried booting with LaCie 2big drives attached and all was fine.

Really annoying but at the least there is a simple workaround.

I have the exact same set-up as you. Try re-installing 15.2 with no Thunderbolt connections attached. This should install the new OS fully. Restart — THEN attach your connections. This has worked for me. The only problem is you will have to start up your computer without any Thunderbolt connections attached, then attach. I'm doing this until there is an update, patch or fix. Hope this works for you as well, happy holidays & good luck!

‚Migration assistant told me it couldn’t use a Carbon Copy Sequoia backup, so I wonder what I did wrong?‘

You cannot do a full restore of a Sonoma system just from a Time Machine backup because Apple changed the way Time Machine works some years ago (it does not backup system files any more).

First, you will need to create a Sonoma install drive (can be a simple USB stick).

Then go into Recovery Mode, wipe your startup disk and boot from the stick and reinstall Sonoma.

Then boot the blank Sonoma system and start Migration Assistant. It will use your Time Machine backup to restore all user files. That even works with a newer backup made under Sequoia (at least it did for me when I finally gave up after almost 8 weeks of trying to live with the many Sequoia hickups).

The only not so obvious part is the creation of the USB installation drive (needs some terminal commands), but there are numerous videos on YouTube to explain the process im detail.

From SoftRaid tech support: "Apple engineering said they found this bug and will be fixing it in 15.3."

I found that I had to disconnect all Thunderbolt peripherals to do the upgrade - drives, hub, and KVM. The upgrade completed and I booted as-is using a BT keyboard and trackpad. Let it run and did all the privacy things. Then I plugged all the Thunderbolt devices back in and the system continued to run.

However, the system will not boot with any TB peripherals attached. I gave up and went back to Sonoma.

For anyone using SoftRAID (or OWC Thunderbolt peripherals, I suppose), they have critical alerts email list, which would have told me to NOT installl 15.2. You can sign up for it here: software<dot>owc<dot>com/support/softraid/

Confirmed with OWC ThunderBay 6 / Thunderbolt 3 with APFS AppleRAID0

This is what I've also found to be the issue. Leave thunderbay off then turn them on after boot. All my drives load fine and worked all day today.

"I also note zero replies or any attempt at help here from Apple. "

This is because Apple doesn't monitor this group, we are just a user to user support group.

In my 20+ years of using and installing macOS I've found that it is best to disconnect peripherals, uninstall any old unwanted apps and to shut down any running apps before initiating the upgrade/update. To date I've had no major issues. It should be remembered that Apple doesn't ensure that third-party peripherals & software are compatible but do release beta builds for developers to try before final release. Not all developers have enough time or enthusiasm to make sure their products are compatible which is why may users decide to delay updating macOS until they are happy that their third party hardware & software are compatible with the new release. Of course there will be first party operational bugs in the release of macOS and these should be reported to Apple using their reporting system.

Many thanks. Very similar 2019 MacPro with the same issues and most persistent are the peripheral issue. Re-installed via Recovery but problematic USB-C ports are powered but not recognizing OWC Elite Pro Dock, nor any HD plugged into the USB-C port.

Thankfully read your post re: reboot first, then plug in external HD and the HD is recognized.

Not ideal but at least a work around until a fix comes out!

mine was the same.

unplug any USBC or TB drives and plug them in once started.

I've had long calls with Apple support ending yesterday when they took logs from my machine to see is going on. will update this thread if they ever bother coming back to me.