How to install apps onto Kodi 17.0 Krypton

Hi! So I have an issue. I have watched all the Kodi installing videos for Kodi Krypton 17.0, however, when the person (the person in the tutorial videos) can install apps in Kodi, I cannot. For example, most of the videos show a guide on how to install “Exodus”. I would follow all the prompts to installing it successfully but when I click to install (“Exodus”) it wouldn’t install. A notification would come up, instead, on the top right hand corner saying (first the name of what I’m installing, in this case “Exodus” then) “Dependency on script.module.elementtree”. I don’t know why the script.module.elementtree is not on my Kodi (or whatever the issue is) but it wouldn’t allow me to install anything. So, how do I fix this so I can install other things in Kodi?