I tried loading Pentagon 1 and it failed to load. After running as administrator it loaded.  Nice one Scook. 

Petagon fails to load because it cannot access HKEY_LOCAL_MACHINE\Software\rgc:audio software\DXi\Pentagon I. Changing permissions on that key or running SONAR as administrator have been necessary since Vista, I believe. 

Any idea why it's no longer bundled with SONAR? I thought it was cool, and the only way to get a Vocoder effect without going third party.

No, was surprised to see it dropped. Pentagon was the only bundled plug-in which needed a registry hack or SONAR to run as administrator. The 64bit version had a pretty nasty problem with the Valleys Simulator used in some of the patches. But both of those issues have been around a long time.

Yeah, I find it to be a shame that Cakewalk seems to have ditched Pentagon in the latest version of SONAR.  It's a reason I still have X3 installed.  Hopefully, Cakewalk will either return it by popular demand, or give us "Pentagon II" that could be an improvement (32 & 64-bit native) over I.
 
Apparently the synth still has its uses as a cool vocoder.

The only way I see it returning is as a brand spanking new VST3 Pentagon II synth for sale.

However with Rapture Pro and Z3TA+2 I'm not seeing what the selling point would be, why would it be unique among these plugins?

I had a HUGE problem with Pentagon when I upgraded to Win7/64. Had the DX and the purchased version and projects that still had it in there wouldn't work at all, and they crashed like crazy. 

Well that's why it didn't return with Platinum then, buggy, and besides it's ancient. New users won't be impressed, old users still have their copy with X3 so should be 'happy'. Onwards..

I prefer Pentagon to both Z3ta and Rapture even though those synths are more powerful. I am a sucker for the traditional analogue synth emulations.
 
Maybe it will turn up as a free legacy synth like Square?

A bit ago Noel pronounced the introduction of "synths" (plural) "soon". Clearly now one was Rapture Pro. I wonder if a remake of Pentagon is in the works - maybe for inclusion in the membership pkg?
I agree though, would love to see a Pentagon update. Not a fan of the Frankensynth approach taken to meld DimPro and Rapture honestly. It's 2015 and I would have preferred to see Rapture developed to compete with Serum, Iris, Diva2, and Alchemy (especially now that Alchemy 2 won't show up in the windows enviro). With the Lean approach Cake seems to be taking in applying their resources to development, I think their future might be better served in smaller, simpler basic synths - solid performers like Pentagon.
Just my 2 cents.