Course should play continually

Do you mean 'resume' from the same place if the learner closes their browser and reopens the course?

I'd so, you can set the course to 'Always resume' or 'Prompt to resume' in the Player Settings.

For a variety of accessibility and security reasons, I'm pretty sure courses can't switch instantly between tabs. You'll always see the standard 'play' button when the course is reopened in a new tab or window. The learner will always have to press play, and when the course is set to Prompt To Resume, select whether they want to start over or continue where they left off.