How can I debug my retrofit API call?

I'm using retrofit to get some data from the Flickr api. The method I'm making the call in looks like this:

public static List<String> getImageIds(int size) {    Call<PhotosList> call = flickrService.getPhotos(apiKey, format, "1");    Log.d("TEMP_TAG", "photo url: "+ call.request().url().toString());    photoIds = new ArrayList<String>();    call.enqueue(new Callback<PhotosList>(){        @Override        public void onResponse(Call<PhotosList> call, Response<PhotosList> response) {            Log.d("TEMP_TAG", "it's getting here");            PhotosList photosList = response.body();            List<Photo> photos = photosList.getPhotos().getPhoto();            for(Photo photo : photos) {                Log.d("TEMP_TAG", "adding photo id to list: "+ photo.getId());                photoIds.add(photo.getId());            }        }        @Override        public void onFailure(Call<PhotosList> call, Throwable t) {            // TODO: Clean up            Log.d("TEMP_TAG", "photoId: ");        }    });    Log.d("TEMP_TAG", "it's getting here too");    return photoIds;}

However it is never getting into the onResponse() method. The first log statement within onResponse() never prints, neither does the log statement in onFailure(). When I try entering the URL that is returned by call.request().url().toString() in the browser it works fine, and I get the expected JSON. Why is my enqueue() method never firing?

Thanks for any help!