Original Photos not downloading automatically - can only manually retrieve them

I must be confused how the downloading process of Photos works. I got a new Macbook and I enabled Photos in my iCloud settings and kept the "Download Originals to this Mac" enabled. I thought that meant the original photos and videos would be downloaded automatically.

But it is stuck at the 20,603 number and hasn't moved at all. The only way I can get it to decrease is by choosing a specific video or photo and that forces the original download for that specific item. So I can do this one at a time -- obviously with that many photos/videos, that is not scalable.

The only other solution I have thought about is to Export All Unmodified to an external drive or something. I assume that would force an original download during the export. But that seems like a roundabout way to get the originals.

Any thoughts here? Why wouldn't these downloads just be happening automatically? I have good internet speed (600Mbps+), I am using ethernet/usb (have also tried wireless), etc.

Am I missing something?

Thanks.