The record
In a post dated February 9, 2018, a user says their HomePod worked otherwise but would not play music. Siri confirmed each request, yet nothing came out, no matter which artist they tried. The setup is described as a HomePod paired with an iPhone X running iOS 11.2.5. The next day the poster reported that signing out of iCloud and back in through the Home app on the iPhone resolved it, a step another participant had passed along from Apple Support. This reflects a single user's experience.
Read the original source at Apple Support Community (opens in a new tab) ↗
A documented user report, not an independently reproduced test or an estimate of how often the problem occurs.