Issue with audio with Alexa on Rpi3 with ReSpeaker 4-Mic Linear Array Kit

Basic commands on Alexa is working fine with good and clear audio, but when I try to play different stations on iHeart radio or TuneIn, it would sometimes play fine but most of the time doesn’t. Alexa acknowledges that it recieved the command and it started playing but there is no audio output. I am using the Rpi 3 with Stretch os with Respeaker 4-mic Linear Array kit, the speaker is connected to the JST 2.0 port on the respeaker.