Ok -  I spent the weekend investigating what was going on, and found the following:
 
[1] The things that weren't working were Cakewalk 32-bit plugins (Breverb etc) and all pro channel modules
 
[2] Other 32 bit plugins were working
 
[3] My X3e installation was 32 bit, running on a 64 bit operating system
 
[4] The "command center" has installed the 64 bit version of Platinum without asking.
 
Evidently Platinum 64 will not run the 32 bit version of Cakewalk plugins via the bridge .  Now, this should not be a problem because the options under VST Settings to hide duplicate 32 bit plugins and to substitute 64 bit plugins for 32-bit ones were both  checked  But it wasn't working.   Although the platinum install has the 64 bit version of Breverb in its vst folder. the FX list was still showing the 32-bit version, and still attempting to load the 32-bit version on existing projectcts.
 
It was also attempting to load the 32 bit pro channel modules .  Often I would get an error that "this preset can only be used in sonar X2 and above."
 
THE FIX;
 
[1] Removed the X3e 32 bit VST directory from the scan list and re-scanned - all cakewalk plugins and pro channel modules then worked
 
[2] Replaced the X3e 32 bit VST directory in the scan list, but AFTER the 64 bit directory re-scanned again
 
[3] now it shows the 64 bit version of the Cakewlak plugins,  and my 32-bit non Cakewalk plugins.  Everything works
 
[4] Phew!

Loving Platinum so far!  Installation was a breeze and it's humming along beautifully.

Install was quick and painless; I actually like the C3 method better.  Picked upright where I left off in the middle of a project started on X3e.  For the first time I left the previous install in place since it didn't seem to claim too much additional SSD space.  So far, after a couple days of constant use have found no probs and plays well with NI 10 Ult, Ozone 6 and various soft synths like Omnisphere, Trilian, Iris2, Absynth, etc. Melodyne Editor registration was not a problem (unlike last time),AD2 likewise.  This is really how it should be-it is such a pleasure to have all this creative power at my fingertips and not have to even think about the process. All totally transparent, immersive, unencumbered and fun.  Thanks!  My only gripe is I still don't get any newsletter, update email or anything to even indicate that this release existed.  I've linked my accounts, etc- In all the years I don't think I've ever received any thing from Cakewalk, not even a postcard;)

This is the Best Version yet Downloading to Running perfect, still got to put it through its paces and record some new stuff can't wait, so far I'm impressed!!

Seamless upgrade...my luv continues to grow...