Apple seems to have taken down the installers for OSX 10.13 or 10.14 from their web site. All the previous links to these installers end up on the OSX 10.15 page. The previous installers I had downloaded report they are damaged, apparently because the "certificate" has expired. I tried at the Apple Store who had no solution. Where have the installers gone? Why has Apple made them unavailable?
MacBook Pro 15", macOS 10.12
They should still be there, the certificate issue referred to Yosemite, El Capitan and Sierra.
How to upgrade to macOS Mojave - Apple Support
How to upgrade to macOS High Sierra - Apple Support
If when you access the App Store pages for these OS's and see Open then the App Store is detecting
a copy of that OS on your mac.
Open your Applications folder and look for Install macOS High Sierra.app or Install macOS Mojave.app
move it to the Trash, empty the Trash.
Connect your mac to your router using a cabled connection rather than WiFi.
Restart your mac, access the download pages again, retry the download, do not use the mac while
the download is in progress, also if other devices share the same internet connection then don't use them either.
They should still be there, the certificate issue referred to Yosemite, El Capitan and Sierra.
How to upgrade to macOS Mojave - Apple Support
How to upgrade to macOS High Sierra - Apple Support
If when you access the App Store pages for these OS's and see Open then the App Store is detecting
a copy of that OS on your mac.
Open your Applications folder and look for Install macOS High Sierra.app or Install macOS Mojave.app
move it to the Trash, empty the Trash.
Connect your mac to your router using a cabled connection rather than WiFi.
Restart your mac, access the download pages again, retry the download, do not use the mac while
the download is in progress, also if other devices share the same internet connection then don't use them either.
It should , but Disconnecting from the Internet & setting the date back to 2014 eliminates the silly untrue error message.
This is an example, there are plenty of others. Another post elsewhere said the 10.13 certificate expired mid-October.
http://osxdaily.com/2019/10/24/fix-install-macos-application-damaged-cant-be-used-error-mac/
Thanks for solving my immediate problem. But the App Store should tell you why.
OK that worked for 10.13, now downloading 10.14. But why does it not tell you that you already have downloaded it, instead of just disabling the download button!!!! You can't believe how much time I have wasted on this, hours and hours. And again the downloads I had, claimed to be damaged because of the certificate problem which is documented by other users all over the web. Arrgh!
Well you should know that have have already made an attempt at downloading.
What was the warning you got when attempting to 'Open' it never mentions expired certificates,
usually just says this copy of macOS ***** is damaged.
Where about on the web are you seeing information about expired certificates for High Sierra and Mojave.
Can't download installers for OSX 10.13 or 10.14 anymore
