Issues with iCloud syncing after updating to MacOS Monterey

Try booting to Safe Mode. That boot up takes minutes and clears caches and other things that may resolve your problem.

How to use safe mode on your Mac - Apple Support

A lot of times just boot to Safe Mode followed by normal boot resolves problems.

I do not believe this is a cache issue but a glitch in the software. After suffering with this issue for months, I was advised to delete all third party apps, VPN and to reinstall the software (Monterey) and still no change. Now after further testing it has to do with my download speed and the size of my data. Plus this problem is reported by others. If you're lucky to resolve the problem in the way you describe good luck, however it seems that the engineers may know about this issue. I've gone in iCloud.com deleted everything under the sun. I have downloaded files to my external hard drive so I can use my laptop. The laptop is basically dead because I cannot access the iCloud Drive files. If I download the files directly back to the laptop the Mac begins trying to upload the files and it is hung.

Yup, I have been suffering since beginning of December. I think there is a software issue.

I've been suffering with this issue since the beginning of December. I did everything including a new installation of Monterey and deleting all third party apps and VPN. Last night after speaking to another senior Mac Book advisor and testing my download speed and looking at the data stored in iCloud.com we came to the conclusion that the data was too much for the download speed and it will take forever to get the data synced. She did say that she has seen reports that we are not the only ones experiencing this issue and we should hear from the engineers shortly. I have no idea what shortly means but for me I'm delaying the purchase of a new Mac Book Pro. I need to have this Mac Book synced so I can migrate the data to the new laptop.