Refer to issue: Roon and miniDSP SDH - Not playing issue (ref#N9DP0U)
I spoke too soon… while re-booting the Roon ROCK solved the issue for that listening session, I have now found that the problem returns each time I power cycle the SDH. The only fix I have found is to re-boot the ROCK after the SDH is powered on every time. Once that sequence is complete, all works OK…
The ROCK does not have to be rebooted to play to another zone (a Roon-ready Escape P6 portable speaker). Only to the SDH. And the SDH plays other sources (AirPlay, direct connected TV, etc.)