Trying to install the Ace plugin for Sigil

Oh, neat! (I said to myself): Within Sigil (an ePub checking/editing tool), you can add a plugin to run Ace (an accessibility checking tool)! …What’s that? (I said to myself.) The plugin doesn’t work on Mac? OK, fine, I’ll try it in Windows under Parallels. [Insert lengthy process of getting Parallels to run on my new computer here. It worked fine on my old computer, but you know how these things…