MacRumors published a story that Apple has released HomePod 15.4.1 Software.

Apple Releases HomePod 15.4.1 Software With Siri Fix

Alongside iOS 15.4.1 and iPadOS 15.4.1, Apple today released a new 15.4.1 update designed for the HomePod and the HomePod mini. The 15.4.1 update comes two weeks after the release of the 15.4 HomePod software.

According to Apple's release notes, the ‌HomePod‌ 15.4.1 software update fixes an issue that could cause some HomeKit accessories to fail to respond when controlled via Siri voice commands.

  Apple Releases HomePod 15.4.1 Software With Siri Fix