"Download" results link leads to blank screen

(I swear I did a search! I read them all! But I didn't find an issue that was the same as mine.)

When I click the "Download" link to get a CSV of the results, I end up on an empty screen. Not completely-blank like an all-white screen, but a page that looks just like the rest of Webform (like "Submissions", say) with no content in the main body.

I am pretty sure that this is not a memory problem, because my form only has 5 fields and there are only 4 submissions. Also I use Webform on a bunch of sites (all on the same server, with the same settings) and I have never had this issue before. Is there any way to get it to print out an error code (or similar)?

Thanks!