The regular release of Firefox 52+ only allows one plugin, which is Flash. So it's normal if other plugins installed on your system are ignored.

The Extended Support Release (ESR) of Firefox 52 will still run Java, Google Talk, and other old plugins. ESR was first developed to meet the needs of large organizations that wanted Firefox to change much more slowly -- but anyone can run it. More information on this change and where to get ESR: Why do Java, Silverlight, Adobe Acrobat and other plugins no longer work?

I might have read your post too literally. Plugins are generally used to embed content into pages. If you were referring to other kinds of add-ons such as extensions, that would be a different issue. Could you describe what's disabled in greater detail?