There seems to be no rhyme or reason to which files this happens to, but some files will have a cloud icon that says "uploading" when hovered over. It never changes from this state, and the right click contextual menu doesn't show for some while others will show "Cannot sync, Ignored item". These are PDFs, Adobe files, and Microsoft Office files, so they don't fall into the known list of ignored items.
When I check the same files on Box.com, most will show up with 0 bytes. I have tried quitting Box as well as restarting my machine. I don't want to log out of Box Drive for fear that these files that exist on my machine but show as 0 bytes online will be lost.
Using OS Ventura 13.2.1 and Box Drive 2.31.64 on MacBook Pro with M2 chip.
This has happened on an M1 chip MacBook as well.