To use the Redux devtools you'll have to install @ngrx/store-devtools and import it in the AppModule - docs.

Install it with:

npm install @ngrx/store-devtools --save 

Import it with:

@NgModule({
  imports: [
    StoreModule.forRoot(reducers),
    // Instrumentation must be imported after importing StoreModule (config is optional)
    StoreDevtoolsModule.instrument({
      maxAge: 25, // Retains last 25 states
      logOnly: environment.production, // Restrict extension to log-only mode
    }),
  ],
})
export class AppModule {}

Make sure you import all modules from the store first before importing the StoreDevtoolsModule in the list of imports.