No input file specified

Hi, I’ve just installed Wordpress and installed Sage using composer, run through the guide and then I went into the newly created theme folder and run yarn run start. All I get is “No input file specified.”, is this common?
Please let me know if I can provide you with any further information. I’ve installed yarn using chocolately on Windows 10 and when I try to access directly using xampp I get a theme with no styling - 404 - and once I run yarn run start and I get proxied by BrowserSync I get the “No input file specified.”.