Unable to turn on iCloud desktop and documents

Try restarting in Safe Mode. This bypasses certain potentially disruptive processes, and it often helps. Safe Mode is different for different computers, so see this: 

           Start up your Mac in safe mode - Apple Support 

Timothy Cole wrote:

Things I have tried:

Restarting

upgrading to sequoia

sign out of iCloud and sign back in

starting in safe mode

creating a new user and signing in

it’s a freshly reset MacBook Pro M1 with just OSX on it and cannot get Dekstop and Documents to turn on or sync

So apparently you have essentially reset the Mac to almost its factory defaults, right? Maybe some old app or preference is still intervening?

My favorite movie quote might apply here: "I say we take off and nuke the entire site from orbit. It's the only way to be sure." -Ellen Ripley, 'Aliens'

So backup, erase, do a clean install and check if it then works as expected. Then restore only data files and one-by-one mission critical apps.

Did you installed any third party apps / softwares / vpn services in newly purchased Mac ? if so uninstall them Uninstall apps on your Mac - Apple Support

Don't use any cleaners , anti virus in Mac check your network speed , if the files that are stuck , may be those files are larger in size or corrupted Work with folders and files in iCloud Drive - Apple Support

Check your iCloud Drive file and folder status on Mac - Apple Support

Timothy Cole wrote:

Anyone from Apple that can chime in? It seems like iCloud is like completely broken for me at this point. Cannot use via a web browser (Tried Chrome and Safari) on any machine (tried two different macbook pros and my imac desktop) and nothing works!

This is a user-to-user forum so contact official Apple support.

If it was me I'd do a plain vanilla clean install (to an external disk) and try again. Or ask another user to try if his iCloud account works via that Mac via his newly created Mac user account. Or try if it works in another location when connected to another Internet service provider via a different router.

Timothy Cole wrote: Things I have tried:

Restarting

upgrading to sequoia

sign out of iCloud and sign back in

starting in safe mode

creating a new user and signing in

…

Good to know. All great things to try.

What do you see at iCloud.com? Does iCloud agree with what you see on the Mac?

In the Find My.app, does what you see make sense?

You say you're are running Sonoma-- is that right? I'd upgrade to Sequoia.