Hello mhd_ahmad_altaf,
Thank you for reaching out to Apple Support Communities.
These steps may help:
" If you can’t move or save a document to iCloud Drive
If you can’t move or save a document to iCloud Drive, your iCloud storage space may be full. The document stays on your Mac, and is uploaded to iCloud Drive when space becomes available.
iCloud Drive shares your iCloud storage with iCloud Photos, iOS and iPadOS device backups, messages and attachments in iCloud Mail (your @icloud.com email account), and more.
To get more space, do the following:
More details can be found here: Use iCloud Drive to store documents on your Mac, iPhone, and iPad
If the issue persists, can you provide a few more details? Are you noticing any other issues with iCloud on your computer? Are you able to save files with other apps like Files or Pages? Also, which Mac and macOS version are you currently using?
Cheers!