Wooohooo it finally worked!!
After copying the plugin files in both directories (engine **AND **project folder), I was able to package the game without the nasty error! 
I’m not 100% sure what I did tho… By copying the pluginfiles to the project folder ALONE I wasnt able to actually acitvate the plugin in the Plugin Browser…
Anyway… it works now!
Thanks a ton for the new file!