icloud drive not uploading large files

How large are the files? iCloud Drive has a size limit of 50GB (iCloud Drive FAQ - Apple Support)

And you should ensure, that the Energy Saver will not put your Mac to sleep, before the file has been uploaded.

Yes. I am trying to upload a 32 GB imovie library that has consumed too much space on my Mac, and it's been stuck at "zero" for days. I have nearly 1.2 TB of available iCloud space.

Apple seemingly just isn't interested in making things work these days - there has been absolutely no end to bugs in the Catalina era.

(And no, I'm not going to try to "compress" it before uploading it; that'd a) be an absurd workaround, b) isn't reasonable when the whole reason for trying to offload the huge file is that I've run out of space... something that, BTW, never happened on my prior Mac laptop, from the era before Apple refused to continue making laptops with magnetic storage... and Apple products "just worked".)

Compress the files https://support.apple.com/en-in/guide/mac-help/mchlp2528/mac

And then upload https://support.apple.com/en-in/guide/icloud-web-only/mmad632d1df2/icloud