Which script am I missing when trying to install framework7 custom build?

npm ERR! missing script: build-core:prod

I'm receiving the above error when trying to run the custom build for framework7 - https://framework7.io/docs/custom-build.html

I have gone through each step however I am running into this problem in cmder and I'm unsure why.

The error occurs at step 7 if this info is of any value

Any help would be appreicated.