Dreamweaver fails to compile scss files

We started working on a site after a while and now when we save a SCSS file it does not compile.

We selected the Autocompile chackbox but nothing happens on file saving.
We also de-selected the checkbox and tried to compile manually by clicking F9 in the scss file but nothing happens.

WHat could be the reason?

Last time we used the files all was OK.

Thanks for any help on this.

Franco