Why doesn't PP recognize some extensions?

I install extensions in two ways—either through ZXP or by simply dropping the folder into C:\Program Files (x86)\Common Files\Adobe\CEP\extensions. But sometimes Premiere just doesn't recognize the extensions. Right now, I wanted to install Linkup Suite!  I downloaded it from the official website, but Premiere doesn't recognize it! It’s a good thing this is the free version—but what if I had bought this extension? How can I get Premiere to recognize the extension?