Macbook Air is not showing up on Find My

If your MacBook Air isn’t showing up in Find My despite setting everything up correctly, there’s a good chance something’s not quite registering on Apple’s backend or a key piece of the setup isn’t behaving as expected.

Since you've already checked the common resources, let's dig into the deeper or often overlooked parts.

First, verify the basics—but thoroughly:

1. System Settings > Apple Account > iCloud > Find My Mac – Ensure it's toggled on.
2. Check Location Services: Go to System Settings > Privacy & Security > Location Services, make sure it’s on globally, and scroll down to ensure Find My is enabled.
3. Confirm that your Mac is linked to the correct Apple Account. Sometimes, if you're using a different user account or an iCloud login that isn't the primary one for Find My, it won’t show up.

Then, here are a few less obvious things worth trying:

• Check iCloud Status: Visit iCloud.com and sign in. If the device doesn't show there either, it's likely not registering to iCloud correctly.
• Network Connection: Your Mac needs to be online for it to show in Find My. Ensure Wi-Fi is connected and it's not behind a firewall blocking Apple’s location/reporting services (seen sometimes with overly aggressive DNS filtering or firewalls).
• Firmware & T2/Apple Silicon Lock: If it’s an Silicon Mac, make sure it’s not in some kind of recovery mode or Activation Lock has been disabled and re-enabled incorrectly. A PRAM reset or reboot into recovery and re-signing into iCloud can help reassert presence with Apple servers.

If everything seems right and it still doesn’t show, try signing out of iCloud completely and signing back in—this can re-register the Mac with iCloud and the Find My service.

Should none of the above helps, your next step would be to contact Apple Support directly for further assistance with this matter. To do so, simply select the "Support" link on the lower left-hand side of this forum's web page.

By virtue of " CleanMyMac Health Monitor " appearing in your above image

Who knows what the " CleanMyMac " application has done and how it is affecting the computer not appearing in " Find my Mac "

Let us just say " BrickMyMac " aka " CMM " has claimed another victim

Any Third Party Applications that will interfere with the normal operation of the OS,  is an invitation for disaster. 

Certain Applications maybe available on the Apple Apps Store - this only means the Developer is prepared to pay Apple a percentage on each sale. 

What the Application may do to the computer is up to the User to check this out before purchase

Any of the below should be removed as per Developers Instructions 

Disk Cleaner 

CleanMyMac , aka “ BrickMyMac “

New macOS Malware "Cthulhu Stealer" Targets Apple Users' Data

Un-Like Microsoft Windows, which does have “ Disk Cleanup “ and “ Defrag “ as part of their Operating System 

Apple does not.

To put the Third Party Disk Cleaner / Optimizer in context and the damages it may have or has already done.

This type of applications can or will Muck Up your User Account ( Home Folder ) of this machine.

It does not touch the Operating System itself unless you consider your User Account ( Home Folder ) as part of the Operating System.

The Operating System is hosed