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MacOS Catalina 10.15.7 Supplemental Update 2 causes circle with a line through it

I use a Mac Pro with an external SSD. Both the internal drive and the external drive have Catalina 10.15.7 installed and I boot from either depending on what software I want to run. 


The second time the computer started up after installing the Supplemental Update 2 on both drives, the screen went to the "circle with a line through it" icon. This was after entering a user password at login. The first time, a restart fixed it. Now it appears to be a constant problem booting from either drive. 



What I see:

Computer starts and reaches the user login screen.

After entering the password I get an apple with progress bar screen.

Then the circle with a line through it screen.



Fixes attempted:


Repeatedly restarting - No longer helps.


Safe mode (shift key held down at startup) - Boots fine in safe mode for the internal drive. (I cannot seem to find a way to do a safe boot for the external drive.) 


Recovery mode (Command R) - Disk Utility found no problems with either drive or any of the volumes. (Followed instructions here: https://support.apple.com/en-us/HT210898)


PRAM reset (Option-Command-P-R) - Sometimes works on the next boot but only for the internal drive.


Clear Caches (~/Library/Caches/ and /Library/Caches/ on both drives) - No effect


Reinstall the OS - It is an overnight download on this internet connection but that is next.



Am I missing anything obvious?

Mac Pro, macOS 10.15

Posted on May 6, 2021 7:55 PM

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10 replies

May 8, 2021 11:49 AM in response to J in CA

Not exactly fixed but now intermittent.


First, I made a stupid mistake. The problem was not Supplemental Update 2, it was Security Update 2. Sorry for the confusion :|


Per HWTech, I went looking for login items. There was nothing in the User part of System Preferences. So I checked:


~/Library/LaunchAgents/

/Library/LaunchAgents/

/Library/LaunchDaemons/

/Library/StartupItems/


Beyond the usual Google stuff, there were several things from a game manager, Gog Galaxy. Trashing everything did not fix the problem. EtreCheck still listed a Login item though, buried in the app bundle for Gog Galaxy. Trashing the Gog Galaxy app seemed to fix things at first. I would love to know how that Login item was still active though. (It is always the games. The open source, volunteer maintained, photo software might crash but it never causes this level of chaos. Part of why I isolate the dodgy software on an external drive with its own OS.)


I would also love to know how having that on an external drive effected my internal drive's OS. I keep the internal drive encrypted so the external OS cannot read or alter it.


It is clear now that the problem is intermittent. I can get either drive to boot by first reseting the PRAM. The next startup usually works. After that, it is back to the same circle with line through it.


EtreCheck results are attached.


I do use FileVault but not a firmware password.


I do not use any third party cleaners or antivirus.


Thank you to everyone for the suggestions so far :)



May 8, 2021 5:32 PM in response to J in CA

Have you tried creating a new user account to see if the issue also happens in the new user account? This will point you to whether it is a user account issue or a system wide issue. I would reboot the laptop after creating the new user account and log directly into the new user.


Have you tried to reinstall macOS over top of itself? I would suggest creating and using a bootable macOS USB installer so that your broken installation of macOS does not interfere with the process.

How to create a bootable installer for macOS - Apple Support


May 6, 2021 8:19 PM in response to J in CA

If Safe Mode boots fine, then it implies you most likely have software issue of some sort. Since the issue occurs just as you log in, then it may be due to a Login Item. Try disabling the Login item(s). You can also test this theory by creating a new user account and rebooting and logging into the new user account. If you still have problems then run EtreCheck and post the report here using the "Additional Text" icon which looks like a piece of paper.


To boot into Safe Mode on the external drive you need to hold down the Option key immediately after startup chime so you can access the Apple boot picker menu. Then as soon as you click on the external drive you need to immediately hold down the Shift key.

May 7, 2021 3:01 PM in response to J in CA

All I can tell you is that I have an iMac Pro, installed this most recent update and soon began to get the same thing: the dreaded prohibitory sign that the Mac can't find a usable operating system. The fix is to boot in Recovery Mode and reinstall the OS. Interestingly, even though this is via Internet and would presumably have the latest version, now that I have done that, I again see this 2nd Supplemental update available. Needless to say, I am not going to install it as I have to assume Apple isn't building it into their current Catalina build because they recognize that there are problems with this update.

May 8, 2021 6:35 AM in response to Old Toad

I am aware. It’s the 2021 2nd security update that I am referring to, that’s not included in the current 10.15.7 online build but is available as an update, and which when installed results in a prohibitory sign.  So, unfortunately I must avoid.  Unfortunately Big Sur has been too problematic an upgrade on my other systems so I prefer to avoid that hassle again as well.

MacOS Catalina 10.15.7 Supplemental Update 2 causes circle with a line through it

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