I see the same issue with FF 52.0 64bit with the OSDS 2.13.9 version available from the Mozilla Add-on site ... we submitted an OSDS 2.14.5 version for release, which is awaiting review release by the AMO team, and this does work with FF 52.0 64bit ... so you would have to wait for it to be released ... or we have a standalone version that can be installed from http://osds.openlinksw.com/#DownloadFirefox