Thank you for your response and apologies for responding late.
I was using runtime.exs having forgotten it was introduced in 1.11 and not in 1.10 so was pulling my hair as to why the configurations were not being read at application start.
Moving the configuration to releases.exs kind of worked, I have specified application port as 4000 but it runs on 16392 which I was not going to investigate yet because of a deadline 
