Hard so say without all seeing the components involved. But most likely your service which injects httpClient is provided in higher than this interceptor in the DI hierarchy tree. This is a nice piece of documentation you can read about DI hierarchy in angular - https://angular.dev/guide/di/hierarchical-dependency-injection.

You can test it very easily. Take the service that uses httpClient, and provide it in your path's providers (in the same array when you provide the http inerceptor). If it works, the issue is what I described above.