Is it a Nyquist (NY extension) plug-in, either this Limiter (Limiter) or this “Soft Limiter” (http://audacity.238276.n2.nabble.com/Soft-Limiter-Nyquist-plugin-for-Audacity-td1516589.html)? Or is it a VST or Audio Unit plug-in?
Does it “fly out” when you try to paste it in the Audacity “Plug-Ins” folder?
Someone else had this problem with a Nyquist plug-in. Assuming you have installed Audacity correctly (see Audacity ® | Download for Mac OS ) I don’t know why this should happen. Might it be some permissions problem (you don’t have permission to write in the place you have put the Audacity Plug-ins folder)? Does logging in as an admin help? I cannot reproduce the issue on my OS X 10.8.2 Mac.
If it is an NY file you can try opening the NY file in TextEdit, copy all the content of the file, then create a new (empty) TextEdit document. In the new document, paste in the copied content, save it on your Desktop with the same file name as before, then drag that file from the Desktop to the Audacity “Plug-ins” folder. See here Nyquist Noise Gate refuses to install on Mac[SOLVED] - #2 by Gale_Andrews .
Depending what the problem is, merely making a non-code change in the text of the NY file and saving that in TextEdit “might” solve the problem. Changing the text between the quotes in the ;info line at the top is safe as long as you only type a to z or numbers.
If you are still stuck PLEASE tell us what version of OS X you are on (as requested at the top of this page). It saves needless guesswork and us having to write out different instructions according to what version of OS X you are actually using (and you having to read it when it’s irrelevant). And of course, tell us exactly what plug-in it is.
Thanks,
Gale