Thanks. I found the FAQ after I had posted. Followed the youtube video and fixed youtube not playing. The new problem I faced was no audio play back from Dorico.
What I had to do was select the voice (Piano) and then further select the output it should use from the drop down. Which was not covered in the youtube tutorial.
Dear Stanek,
What you describe here is manual attribution of sounds to instruments. Dorico can perform this task automatically, when you go to Play menu>Playback Template and choose a template (HSSO+HSE should be default).
Hope this helps!