Unable to use the SharePoint Site option in 'other file storage' when the source is a subsite

This seems to have stopped working back around August of last year.  If I enter a site collection URL in a new SharePoint Site file source, and go through the admin consent steps, it works great.  However, I have a ton of subsites (I know, we're in the process of converting those to site collections) that I can no longer connect to.  I enter the subsite URL, get prompted for my credentials, then I'm taken back to Acrobat where I get a 'access denied: you might not have permissions to access this network resource' message.  The subsite has unique permissions, but I am in the Members group of the subsite.