可以參考以下解法，我的機子是m1 pro 14吋，遇到12.1無法升級的問題。
依據這個網址，昨天升成功：
https://9to5mac.com/2021/12/14/some-users-are-not-seeing-the-macos-monterey-12-1-update-on-m1-macs/
簡而言之，找到「活動監視器」APP，搜尋UpdateBrainService，找到就「強迫關閉」，再去升級；如果第1次不成功，再找一次和強迫關閉一次。幾次過後，12.1會冒出來，也就能成功升級了。
蠻怪的BUG。。。
1.) Open System Preferences > Software Update. Confirm that no update is available, and leave the window open.
2.) Open Applications > Utilities > Activity Monitor.
3.) Go to View > All Processes
4.) Search for 'com.apple.MobileSoftwareUpdate.UpdateBrainService' . Select it and click Force Quit.
5.) The 12.1 Update should appear in System Preferences. Click Update Now.
6.) The update may not download - force quit the com.apple.MobileSoftwareUpdate.UpdateBrainService again using Activity Monitor to start the download.
從 APP 打開
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