Cubase LE 9.5 won't install from Download Assistant on Mac

I have a Mac running High Sierra and have installed the download assistant. However after I have downloaded Cubase LE 9.5 it won’t let me open it for installation. I get the error:

There is no application set to open the document

I have attached a screen shot that also shows the Mac’s info - it’s running High Sierra 10.13.6


HI and welcome,

To me it seems the download has not been finished.