Unable to build and run the frontend on my mac

I purchased the Angular Material Java/Spring E-Commerce - Personal license. I am unable to run the frontend on my mac. It gives me the following kind of errors,

Error: ./src/app/pages/forms/buttons/buttons.component.scss
Module build failed (from ./node_modules/postcss-loader/dist/cjs.js):
Error: Cannot find module 'autoprefixer'
Require stack:
- /Users/rubeshmehta/postcss.config.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/postcss-loader/node_modules/cosmiconfig/dist/loaders.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/postcss-loader/node_modules/cosmiconfig/dist/ExplorerBase.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/postcss-loader/node_modules/cosmiconfig/dist/Explorer.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/postcss-loader/node_modules/cosmiconfig/dist/index.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/postcss-loader/dist/utils.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/postcss-loader/dist/index.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/postcss-loader/dist/cjs.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/loader-runner/lib/loadLoader.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/loader-runner/lib/LoaderRunner.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/webpack/lib/NormalModule.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/webpack/lib/NormalModuleFactory.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/webpack/lib/Compiler.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/webpack/lib/webpack.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/@angular-devkit/build-webpack/src/webpack/index.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/@angular-devkit/build-webpack/src/index.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/@angular-devkit/build-angular/src/dev-server/index.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/@angular-devkit/architect/node/node-modules-architect-host.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/@angular-devkit/architect/node/index.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/@angular/cli/models/architect-command.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/@angular/cli/commands/serve-impl.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/@angular-devkit/schematics/tools/export-ref.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/@angular-devkit/schematics/tools/index.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/@angular/cli/utilities/json-schema.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/@angular/cli/models/command-runner.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/@angular/cli/lib/cli/index.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/@angular/cli/lib/init.js
- /Users/rubeshmehta/java-material-ecom/frontend/node_modules/@angular/cli/bin/ng
at Function.Module._resolveFilename (internal/modules/cjs/loader.js:1085:15)
at Function.Module._load (internal/modules/cjs/loader.js:928:27)
at Module.require (internal/modules/cjs/loader.js:1145:19)
at require (internal/modules/cjs/helpers.js:75:18)
at Object. (/Users/rubeshmehta/postcss.config.js:3:5)
at Module._compile (internal/modules/cjs/loader.js:1256:30)