Bingo--Got it.
Although each "new" servo would work alone--neither would work connected to the Y harness. After checking and re-checking I found that one "new" servo, for whatever reason ,would not operate on the Y connector--replaced it and -Viola.
Thanks to everyone's reply.
I hear you JP, you're so right about not checking the obvious--like when a light is not on in your house you may want to check the switch. .I might add my 1st RC system was a Galloping Ghost --bought back in 1972? . Over the years, both my work and hobbies have equipped with a good understanding of electrical system and how to TS, however this one bugged me.
Still not sure why the one servo does not work on the Y. However, had I known the values I would have been able to check the resistance on each servo and I think that would have given me a clue.

Just hated to have to tear my wing apart to check and replace servo--building my 1st Giant scratch build using a new ST3500 I've had in the box for years..
Again
Thanks everyone!