Trying to start Sikuli server opens FilZip window instead

In order to speed the start and execution of Sikuli actions, when performing many sequential actions, I was advised (a year or two ago) to start the Sikuli 'server' first, using this command:
"C:\Program Files\SikuliX\sikulixide-2.0.4.jar" -s

That worked fine until some days ago, when instead of starting the server and allowing me to execute Sikuli actions, it simply opened a FilZip pane for sikulixide-2.0.4.jar. Here's a screen-shot to show what happens:
https://drive.google.com/uc?id=1wcIMnqpaMUBcT37cnuUn3iHt-fq7suve&export=download

I'm running Win7Pro64. I can't think of any system or software changes that might have affected SikuliX.

Any suggestions would be much appreciated.

DanielF