Having the same issue.
Tried deleting these files to get them reloaded:
XManConfigV2.xml in C:\ProgramData\Adobe\Extension Manager CC\Configuration
ExMan.db in C:\ProgramData\Adobe\Extension Manager CC\Configuration\DB
After that got 1 of the extensions working, which was not appearing in PS before.
Yet I have another extension which is successfully installed yet still not showing up.
I have the latest version. PS CC 14.2.1
Flash based extensions are not supported by PS CC 2014 anymore. Please refer to http://blogs.adobe.com/photoshopdotcom/2014/04/photoshop-spring-cleaning.html, http://blogs.adobe.com/jkost/2014/06/installing-the-2014-release-of-creative-cloud.html
And http://blogs.adobe.com/crawlspace/2014/06/2014-release-of-photoshop-cc-faq.html#plugins (scroll down to "Why don’t my 3rd Panels show up in the 2014 release of Photoshop CC? What happened to Oil Paint, Mini-Bridge & Kuler?”)
If some extensions are not supported by PS CC 2014, you have to continue to use them in PS CC until their HTML based counterparts become available.
Extension Manager has no knowledge which extensions are CC2014 compatible or not, because it's impossible to embed a database in Extension Manager to record the compatibility information of ALL versions of ALL extensions. The authors of extensions declare the compatibility information via mxi file or manifest file within the extension package, and Extension Manager retrieves this information and installs them. The authors didn't anticipate that the Flash based extension support would be removed in PS CC 2014, so the extensions still declare they support the version higher than CC. As a result, Extension Manager installs these extensions for CC 2014 (copy all files to correct location), but PS CC 2014 will not load them. This is why EM lists them but you can't find them in PS CC 2014.