When trying to restore Him pod error :The HomePod software update server could not be contacted. An unknown error occurred (-39).

Hello

I removed two (stereo paired) home pods from my home app because it was reporting that they were not responding, so following apples steps here Reset HomePod – Apple Support (UK)

All have been unsuccessful so I am on the final step which is to unplug and plug them into my mac

When I click the restore HomePod I get the error:

"The HomePod software update server could not be contacted. An unknown error occurred (-39)."

Anyone know how to resolve this