From LR, I selected several images and selected the noted command.
Focus shifts from LR to PS and then just sits there. No further activity.
No dialog boxes either, for either LR or PS.
SO: PS gets some sort of wakeup notification.
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Never mind. It seems a version upgrade was not smoothed out, so machine specific preferences (whatever they are) tripped up PS. Killing PS and restarting it got it working, along with the annoucements about all the new wonderful stuff.
Suggestion to Adobe: if the formatting of a supporting file changes, then the follow on versions either need to translate to the new format OR AT A MINIMUM INFORM USERS TO QUIT AND RESTART.
So this is an upgrade compatibility bug.
Thank you.