On Heroku: Command "webpack" not found - brownfield-team/anacapa-github-linker GitHub Wiki
It's a buildpack thing.
Fixing with Heroku command line:
heroku buildpacks:add --index 1 heroku/nodejs --app brownfield-dashboard-qa
heroku buildpacks:add --index 2 heroku/ruby --app brownfield-dashboard-qa
Fixing with Heroku Web Dashboard
Go to the settings tab, and under Buildpacks, make sure that you have:
- heroku/nodejs
- heroku/ruby
That's what the working version has.