This posting is older than 6 months and can contain outdated information.
Remote Buddy added support for Plex 0.9.5 - which identifies as a completely new application and is also different in many other details. This goes as far as that the very commands that need to be sent to Plex 0.9.5+ and pre-0.9.5 versions differ, making the two versions mutually exclusive. It's only possible to control one of the two versions - and this decision has to be made right at startup. Since this has been discussed before, please also see my previous post on the topic here for more info: http://www.iospirit.com/support/forums/remotebuddy/singlethread/15855/
In your case, I guess this is what is happening:
1) You have both a 0.9.5+ a pre-0.9.5 version of Plex installed, while only using the pre-0.9.5 version.
2) At launch, Remote Buddy 1.19.2 - which has added support for 0.9.5+ - detects your 0.9.5+ copy and concludes that since it has to make that decision and since you have that newer version installed, that's what you want to control.
3) You launch the pre-0.9.5 version of Plex.
4) Since that pre-0.9.5 version of Plex has a different bundle identifier than 0.9.5+ versions, it doesn't get recognized.
5) The Default Behaviour is picked. It has the "Eject" action mapped to the "Right" button by default.
Solution:
If what you want to use is a pre-0.9.5 version of Plex, please remove any copies of Plex 0.9.5+. Then relaunch Remote Buddy, so it can detect your pre-0.9.5 version, select it for control, and control that.
Best regards,
Felix Schwarz