Using the front panel On button or the remote, I could not turn it on today. This has never happened before. But after I flipped the back panel power rocker switch off and on, it booted up just fine. Then I was able to turn it off and on normally from the front or the remote.
All sorts of devices that run off computer chips need to rebooted occasionally. As long as flipping the back panel switch solved it, I wouldn’t worry. If it happens repeatedly, then I’d contact PSA service.
I’ve had a Mk II for just a couple of months and no power issues, but I have a PST (SACD transport) that does this occasionally. I put everything on stand-by at the end of the day and turn on with remote in the morning. Occasionally the PST does not respond and stays dark. A quick off-on of the rear switch solves it. Could be same issue with your DS Mk II. “What” the issue is is a mystery …