macOS sequoia 15.2 update Mac Pro 2019 failed

I do also get immediately after booting back from the 15.2 upgrade the same screen, but disconnecting everything made the 2019 Mac Pro to boot. But I can confirm that even a Sabrent16 ports USB 3.1 HUB (from Amazon) and OWC Thunderbolt 3 Dock do not work anymore after upgrading. No matter where you connect it (USB or TB).

This is a real problem if you have many external device to connect to the Mac Pro.

Boot issue appears to be fixed in macOS 15.3 (24D60)

My suggestion ( meaning it worked for me) build a 15.1 Install on a stick. Boot from that. Erase the Hard drive. Install 15.1. Then use migration assistant to get all your stuff back. All my thunderbolt devices work perfectly once I got back to 15.1. GOOD LUCK !

I had this exact issue. I used screen sharing on a 2nd mac on the same network and i was able to connect to the mac with the problem and found a desktop that was up and running -- just not showing on the actual monitor. I was able to continue my troubleshooting from there (i.e. i shut down, booted into safe mode, etc, reset pram and have at least for now solved that problem. I am still having other thunderbolt issues with a blackmagic multidock that I am still working on.

Same problem. I have a 2019 Mac Pro with one OWC Thunderbay 4 and one Thunderbay 6 attached. After updating to macOS 15.2, cannot boot my 2019 Mac Pro. Tried booting without the Thunderbay enclosures attached, then attaching them after boot but none of the drives will mount. Apple - you've just bricked my whole photography business as all of my photos and videos are on external drives in Thunderbay enclosures. Are you listening?

This is what I wrote to Apple in the kernal panic note:

Something is SERIOUSLY WRONG in Sequoia regarding PERIPHERALS! I had no issues with my USB Hub or any Thunderbolt 3 connections with Sonoma. Now, it’s a mess! I can’t start up with ANY peripherals connected at all. Once my 2019 Intel Mac Pro has started up, then (and only then), can I plug in any hubs or Thunderbolt connections.

I don’t know what happened but Sequoia 15.2 has broken peripheral connections big time!

I'm really stunned that a point two version (Sequoia 15.2) has created such a mess with peripherals.

Sequoia is a disaster.

I can't startup with anything plugged in except a keyboard! After startup, it still has trouble with recognizing my Blackmagic SSD Raid and a simple 16-port USB hub with several hard drives connected. Sonoma does not have this issue and I just created a Sonoma boot drive after upgrading to Sequoia just to confirm everything connects properly. Results: Fine when in Sonoma but in Sequoia, external peripherals either aren't recognized or actually cause a kernel panic.

What a mess.

SoftRAID tells me that this won't be fixed until 15.3. Meanwhile, how the @&*$*%@ could they not test something like this? My MacPro and Thunderbay enclosures are under my desk, with appropriate-length cables. So I have to crawl under my desk with a flashlight in my mouth to unplug everything (2x Thunderbay, KVM, one TB monitor, and a Thunderbolt hub). Then swap to a BT keyboard to boot.

Sorry, not gonna happen and I went back to Sonoma.

On my 2019 MacPro even 15.1 did not run reliably. I had frequent crashes in Final Cut Pro and Compressor. After heavy disk operation, my TB drives got disconnected and I had to reboot to get them recognized again.

My best advice is to invest half a working day and revert to 14.7., which has been totally stable and reliable for me. There are hardly any new features in 15.2 for the 2019 Mac Pros anyhow as all of the AI stuff will only run on Apple silicon.

OWC Thunderbay 4 drives not loading after 15.2 update. I've never encountered issues prior. All drives are APFS formatted. They load fine on MacBook Pro with Mac OS 15.1.

Anyone else with OWC Thunderbays might want to follow this advice which I came upon after the fact...from OWC blog: "When you upgrade to macOS 15.2, I suggested you complete the upgrade while the enclosure is disconnected from your Mac and then reconnect it once the upgrade has completed. This will ensure that your Mac will run correctly during the upgrade process."

My 2019 macbook pro running 15.1.1 also does not want to install 15.2. My first attempt it downloaded the update and got to "Preparing..." but after several minutes produced an error message that stated "Could not finish preparing." My second attempt it downloaded the update again and got past "Preparing..." shutdown the laptop and then made it to the black screen showing progress. After several minutes (during which I was not watching) it asked me to login. This is common in the middle of updates. But once I logged in it appeared to be done. I then checked and it was still running 15.1.1. No error message. It just simply did not install 15.2. I then tried a third time and it was in the process of downloading (for the third time) the update. I thought better of this and canceled the update entirely. I've never had this experience with any update in the past.

I just went back to Sonoma (14.7).

The process is quite fast though not simple (you will need to create a bootable install drive).

Took me 4 hours all in all but only half an hour was actual work. The rest was just waiting for the restore to finish.

Really nice: Apple‘s migration assistant can use a Sequoia-Backup to restore the latest data into your new/old Sonoma installation. So you will not lose anything if you have an up to date backup.

After having some time to do a re-install, I've wiped and reinstalled 15.2 on my Mac Pro...wanted to go back to 15.1 but did 15.2 without thinking and since I started the process I wanted to test the outcome. To my surprise OWC thunder bay drives load on boot with thunderbolt 3. I've restarted and did cold boots many times without issue. Still having speed irregularities with USB-c connected SSDs (Samsung T7 and T9). NOTE this was a clean install not from TM backup and with minimal software installed (Adobe CC, Wacom and a couple of font apps). This could be just a fluke but either way 15.2 has issues for sure.

So at the advice os this guy on macrumors. I gave 15.3 RC a shot and believe it or not it works with my 2019. Your mileage may vary but give it a shot !