First, make sure you have the link to download the latest plugin enabled in your Accesspoint. Go to the QlikView Enterprise Management Console, System, Setup, QlikView WebServers, Accesspoint, and check "Show link". Apply and from your computer, download and install the new version of plugin. You're likely to have installed the old version of Plugin if you haven't updated.
In any case, since they are different versions, I'd re-install your development version in a different folder if possible, so they can coexist.
Hope that helps.