Hey! Both the demo and the full version include the MiniMetersServer Plug-In. The VST3 and AU get installed to their respective folders in /Library/Audio/Plug-Ins. So first double check they are in there. If they are not, try reinstalling. I just checked here and the latest installer does place them there.
In FL Studio, try to go to the Options menu > Manage plugins. Make sure that those folders are listed in the Plugin search paths, then rescan to see if MiniMetersServer shows up.
Let me know if you need more help,
Joe