Icloud drive isn't syncing "sycned" files

I've been using icloud drive exclusively to share files with my windows PC, macbook, ipad pro and iphone.

Recently, I added a number of files to the drive (sum ~100GB) via my windows PC. After about 3 months of waiting, none of these files have synced, and I've noticed some other folders in my drive are now no longer syncing either.

Further, some files which have been synced in the past, are no longer synced - and there are some files which say they are synced on my windows PC, but are not synced to any of my other devices.

On top of all of this, there is extreme discrepency in the synced files when I compared my mac, phone and online drive accessed via chrome.

All of my devices have syncing enabled, and are on the most recent versions. This all USED to work flawlessly. I pay for the 2TB teir, so storage limits are not an issue.

Any ideas of why this is an issue and how I should go about fixing it? Or is it time I go elsewhere?

Thanks,