Getting 404 error when launching playground

Hi @Tanya Agarwal,  

A 404 error when launching a Trailhead Playground is often caused by a temporary provisioning issue, expired session, or a problem with the Playground itself. Try logging out and back in to Trailhead, clearing browser cache/cookies, opening the Playground in an incognito window, or reconnecting the Playground from Trailhead Settings. If the issue persists, create a new Trailhead Playground and test whether it launches successfully there. 

Thanks!