iCloud Drive not uploading files
I recently moved a large amount of data -- tens of gigabytes in tens of thousands of files -- onto my Mac Mini. My Mini is about a year old. It's ARM-based. It has 8 gb of RAM, and tens of gb of free storage on its SSD. I'm running the current version of macOS Ventura, version 13.5.2. I use iCloud Drive, and have hundreds of gb of free space there.
When new files are placed onto local storage on the Mini, a process running locally uploads copies of those files to iCloud Drive. In this case, that process seems to have stalled completely. If I look in the Finder, I see a small circle to the right of "iCloud Drive". That circle has a wedge darkened, indicating that it is part way through the upload process. If I hover over that circle, it turns into a question mark. If I then click on it, I get a "gas gauge" displaying progress to date. There has been no progress in several days.
I have no idea why this is happening and I have no idea what to do about it. As far as I can tell, no relevant resources -- local CPU, storage, or RAM or remote storage -- are currently bound by their constraints. My internet connection is perfectly healthy. I've tried rebooting (several times) to no avail.
Any help?
Mac mini, macOS 13.5