Notes sync issue

See a thread Can’t find my iCloud notes - Apple Community

For your Mac book air it should be updated see the articles Update macOS on Mac - Apple Support

Keep your Mac up to date - Apple Support

Make sure all the devices should be signed in with same Apple ID say example1@icloud.com and its password on the same network use usb cable to connect devices .

See the article Intro to syncing your Mac and your devices - Apple Support

Should I choose to automatically sync all my content or only specific items?

• Automatically sync all content: This is the quickest and easiest option. Simply select the “Automatically sync when this [device] is connected” tickbox in the General pane, then turn on syncing for each type of content you want to sync. Your Mac and iPhone, iPad or iPod touch update to matching content whenever you connect them.
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• Sync specific items: You can also select specific items to sync. For example, you can sync just certain films to your iPhone which can save storage space. You can still automatically sync all items for other types of content, such as podcasts, TV programmes and books.

Do I have to connect my iPhone, iPad or iPod touch to my Mac to sync?

No. If you have an iPhone (with iOS 5 or later) or iPad, you can sync when your Mac and device are connected to the same Wi-Fi network. To set up syncing via Wi-Fi, you must first connect your device with a cable, select your device in the sidebar and turn on the syncing over Wi-Fi option. See Sync content between your Mac and iPhone, iPad or iPod touch over Wi-Fi.

Hello, please see this post too :

iPad note app not uploading - Apple Community

I contact Apple Support yesterday to raise the problem.

I also try this on my ipad who won't upload Notes :

deactivate the iCloud notes then reactivate them again and don't close the Notes app and the upload works again.

Very annoying

Same problem to me. I tried various things: log out on all devices and log in, but it doesn't work. Theres no issue for many years, and it is first time to me, and I can not handle it.