I had this problem when using the iCloud for Windows app that I downloaded from the Microsoft Store. Not only was I getting the not enough storage message, every time I went into settings, it would change the iCloud folder location on my PC from the one I specified to the app default in the Pictures library. Super annoying! This created problems for me because I'm already syncing that library to my Google Drive so I'd be using double the cloud storage for any photos taken with my iPhone.
I ran into another problem with a different Microsoft Store app that was remedied by using the version from the app's website instead, so I thought I'd try that here with the version downloaded from Apple's website.
But, before I could install the Apple website version, I was forced to install Windows Media Feature Pack. Of course I couldn't find the correct download for my Windows 10 version 1909 (Oct or Nov 2019 update I think) because it's not even out yet. But, using the instructions here from GaryS25, instead of the Media Feature Pack, I just tried Windows Media Player under Add a Feature, thinking there might be enough media codecs or other goodies in there to make the iCloud installer happy. It actually worked for me and I now have iCloud syncing to my PC. The settings also seem more complete than the version from the Microsoft Store.
