Opening SW files in Finder

Hi, I'm using SW 2017 on an iMac (OS Sierra), using Parallels Desktop 12 and Windows 10.

I am having an issue when opening files through Finder, and can't seem to find a solution.

What I want to be able to do is choose a file (SLDPRT, SLDASM or SLDDRW), double click it, and it open in the SW application.

This works for the first file I choose, but every time I try it on another file it opens a new SW application window (rather than opening it in the already-open one).

Is there a way to fix this? I never had this problem on the previous version I was running, but this was on a different OS, Parallels, Windows and SW, so I can't work out which one is causing the issue.

Any advice would be greatly appreciated!

SolidworksGeneral