Eleventy build command - is "npx @11ty/eleventy" correct?

Hi. I’m trying to deploy my first attempt at a 11ty site to Netlify but my build command keeps bombing out with a 127 exit code, i think this is related to what you guys have described but i could do with a hand from someone with a bit more experience.

Error is : Command failed with exit code 127: eleventy

Build command is set to : eleventy

package.json contains:

“scripts”: {
“test”: “echo “Error: no test specified” && exit 1”,
“build”: “npx eleventy”,
“serve”: “npx eleventy --serve”,
“debug”: “DEBUG=* npx eleventy”
},

Also my publish dir is : publish: /opt/build/repo/_site
But i specified _site in the Build settings on Netlify.

Sorry for the newbie questions.