Trying to Update WP Smush Pro, cURL error 7:

Trying to update WP Smush Pro and getting "Download failed. cURL error 7:" (and that's it, no more to the error). I checked our server's firewall, and the IPs I found for WPMU Dev are not listed as blocked. I also cannot update WP SMush Pro through the Hub, although I can update other, non-WPMU plugins through the Hub.