If it doesn't work for you, I've checked it, and the problem is that this addon doesn't like query strings in URL (interrogation and all that follows). You must access Chrome Web Store through Opera; if it doesn't show green colour at gear or extensions don't show "Add to Opera" button, then, click in URL shown in search bar, delete "?hl=" (where "" is your location) and press Enter. The page will reload and then wil show properly all the options for Opera. Easy trick!!

If it doesn't work for you, I've checked it, and the problem is that this addon doesn't like query strings in URL (interrogation and all that follows). You must access Chrome Web Store through Opera; if it doesn't show green colour at gear or extensions don't show "Add to Opera" button, then, click in URL shown in search bar, delete "?hl=" (where "" is your location) and press Enter. The page will reload and then wil show properly all the options for Opera. Easy trick!!