Download based on manual time may fail, especially on older systems where the system time is not set right. Go to Apple menu -> System Preferences -> Date and Time and select the closest time server to set your time, and do so. The rest of the Monterey compatible Macs needed a minimum of Yosemite. Only the Mac Pro desktop tower from 2013 is 10.9 compatible and can be upgraded to Monterey. The rest of the Big Sur compatible Macs shipped with Yosemite or later. The iMac with the Machine ID 14,4 and the MacBook Pro Late 2013 and Mac Pro desktop from 2013, and the MacBook Air 2013 with the Machine ID 6,1 are all the oldest Macs of that series that can be upgraded to Big Sur from 10.9. They are 4 years apart in the compatibility and many Macs are not compatible with Big Sur that are with older systems. 10.11 is NOT to be confused for Big Sur, 11.0. The computers themselves that can be upgraded to 10.9 are the same computers that can be upgraded to 10.11 El Capitan. Pretty much anyone who can upgrade to 10.9 can upgrade to 10.11, unless they have some software or driver that has not been rated for 10.11 El Capitan. If you are using Mac OS X server, please check: Server forums These tips all refer to the client version.

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