DeepL plug-in not working under Studio 2017

I cannot activate the plug-in despite following all the installation instructions. The plug-in is on the plug-in list but when added in project settings it is highlighted in orange and the following fly-over message is displayed: "The translation provider required for this entry is not installed on this machine". No MT results are available. The language pair is EN-PL. I will appreciate any hints how to work around this problem.