Hello brinkeguthrie,
We have a great support article that might help with this. Please take a look at it here: Store files in iCloud Drive on Mac - Apple Support. Take a look at this section:
"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, and more.
To get more space, do the following:
Also, we advise that you restart your Mac (Shut down or restart your Mac) and make sure it's fully updated (Update macOS on Mac). Once those are done, please test this issue.
If the issue persists, continue by testing to see when this behavior occurs. First, put your Mac into safe mode and test. Booting into safe mode will disable any startup and login items from automatically opening, which can help us to isolate the source of the issue further. When you do this, you’ll see some unusual behavior from the display; this is to be expected. Please follow the steps in this article: How to use safe mode on your Mac.
Next, let's see if this behavior persists in a new user account on your Mac. Testing in a new user will determine if you have a system-wide issue or if it's user-specific. Please follow these steps to make a test account that can be deleted later: Change Users & Groups settings on Mac. Once the new user account has been set up, log out of your own account then into the new one to test the issue.
We hope this helps. Let us know if we can assist with anything else at all. Take care.
