“Not Acceptable” error message

I’ve been using Download Manager for a long time on this site with now issues, but recently, when I try to access instances where the download is an external site, I get the following error message:

Not Acceptable!
An appropriate representation of the requested resource could not be found on this server. This error was generated by Mod_Security.

WP and the Plugin are both the latest version. You can see an example here:
https://www.cwlc.org/download/housing-discrimination-harassment-and-your-rights-2020/