(Retrofit) Could not locate converter for class crashing app

I was facing the same issue. I fixed it by adding :

compile 'com.squareup.retrofit2:converter-gson:<latest-version>'

to my build.gradle

Then specify the converter when creating my Retrofit instance.

Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(Constants.API_BASE_URL)
            .addConverterFactory(GsonConverterFactory.create())
            .build();