Angular 4.3 Interceptor not working

Source: https://stackoverflow.com/questions/45418477/angular-4-3-interceptor-not-working

TL;DR Make sure there is one import of the HttpClientModule in the entire app (recommened) or provide valid interceptor configuration for each one (ofc for testing only).

Make sure that HttpClientModule is not imported multiple times across different modules of the app. I had it imported in lazy loaded modules. Each import creates a new copy of HttpClient using configuration from the module where it is imported, so interceptors provided in a root module are overwritten.