IRIS OCR plugin not available

I installed IRIS today to work on a scan of a Chinese pdf file. Although all the files appear to be in the 'unpacked' folder (in a folder called IRISaddon), the plugin is not displaying in my list in Studio 2017, and when I try to select it in the PDF file settings it pops up the dialogue box asking me to download it from the Appstore. I've restarted Studio a few times and tried reinstalling the plugin but no change.