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macOS 10.15.5 has downloaded but won't install.

I have downloaded the update and attempted to install the update about 6 times now, machine will go straight into booting screen and restart as normal with no update. I have used the SMC and NVRAM combination to refresh the system but will still not install? is anyone else having this issue?

MacBook Air 13″, macOS 10.15

Posted on May 27, 2020 5:59 AM

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Posted on May 29, 2020 4:54 AM

Well. Funny story.... Had a long chat session with Apple and we discovered I had a huge backlog of purgeable data which wouldn't delete. when you access storage from the apple it said about 38GB available which should be enough to do the update... but when you access disk utility, it said I only had 13.74GB which I found strange. I downloaded omnidisksweeper to find out what files taking up the space, deleted what I could from cache files, backups, photos, etc. but still couldn't get the update to work!!!


Tried using internet recovery which seemed to work but once it go to around 38 mins remaining, I will get a error message saying could not install Mac OS. rebooted and got the prohibited sign! luckily all my important data is backed up, I didn't have a heart attack. Machine went into a boot loop! So went back to square one, alt command R and used disk utility to wipe the drive and start over.


Took 3 attempts but it finally worked, I now have 10.15.5. These things happen. I have had my machine for 3 years with no glitch so I am happy that I was able to revive it with minimal error. Long story short, purgeable data can cause an update to fail. make sure your hard drive is regularly cleaned from cache, old backups and unnecessary old update files which take up a lot of space.

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Question marked as Best reply

May 29, 2020 4:54 AM in response to michaele1

Well. Funny story.... Had a long chat session with Apple and we discovered I had a huge backlog of purgeable data which wouldn't delete. when you access storage from the apple it said about 38GB available which should be enough to do the update... but when you access disk utility, it said I only had 13.74GB which I found strange. I downloaded omnidisksweeper to find out what files taking up the space, deleted what I could from cache files, backups, photos, etc. but still couldn't get the update to work!!!


Tried using internet recovery which seemed to work but once it go to around 38 mins remaining, I will get a error message saying could not install Mac OS. rebooted and got the prohibited sign! luckily all my important data is backed up, I didn't have a heart attack. Machine went into a boot loop! So went back to square one, alt command R and used disk utility to wipe the drive and start over.


Took 3 attempts but it finally worked, I now have 10.15.5. These things happen. I have had my machine for 3 years with no glitch so I am happy that I was able to revive it with minimal error. Long story short, purgeable data can cause an update to fail. make sure your hard drive is regularly cleaned from cache, old backups and unnecessary old update files which take up a lot of space.

May 27, 2020 4:53 PM in response to Harrison3520

Most likely, you do not have enough space on your HD. I’ve had the same problem before and HD space is always the problem. I needed to clear about 18GB to succeed after the same problem. The system used to tell you there was not enough space and how much was needed. Not anymore. It’s just downloads and when you restart to install, it just starts up as usual without doing the install.


Clear some space and I bet your problem is over.

May 30, 2020 12:13 PM in response to michaele1

Sorry, you lost your bet. I have an MP Pro13, Mid 2014, currently running 10.15.3 and the normal system update procedure would not install 10.15.5. I could trigger the installation and after reboot the Apple logo appeared with the progress bar, but it wouldn't go through. After 3 seconds the screen turned black and the MB did a normal boot with 10.15.3. No error message at all.

I the downloaded the Combo Update for 10.15.5, the installation started with 28 GB of free space. The result was exactly the same. The (combo) update wouldn't work, even with enough free space. The problem must be somewhere else.

macOS 10.15.5 has downloaded but won't install.

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