There were some fairly substantial changes made from PE10 to PE11 so my first question would be... does the vst vendor SAY it will or should work, or do they say there will be an update?
It's a free plug-in. I was actually a bit surprised it worked with PE10.
Well, I would go back to the web page where you found it, and check to see if there is a newer version
I do not have a MAC machine now, but on my Windows machine, the folder is Program Files\Adobe\Adobe Premiere Elements 11\Plug-ins\en_US\VSTPlugins
Is there no VSTPlugins folder on MAC for Premiere Elements 11? Was it there for PRE10?