Hi @quantummechanic,
Nice to e-meet you in our Community!
Happy to help clear up this issue, since it must be a very large item (definitely over 10,000 files, and/or larger 20GB) so it cannot be downloaded in one go.
What to do is sync the files to a computer using the Dropbox desktop application instead as the only limit there is how much space you have on your side to fit the download.
If you click on the "Save to my Dropbox" option, they'll immediately start syncing to your computer.
Let me know if you have any trouble at all getting the desktop app!