So I tried uninstalling all Cakewalk products, deleting all cakewalk directories, and downloading command center again. When I do so, I got this error:

After which I went into Windows Add/Remove Programs and did an uninstall=>repair on the latest x64 C++ Redist, as above. That allowed Command Center to install. Using the fresh install of command center, I then reinstalled Sonar. That went off without a hitch. When I launched the app from Command Center though, I got the error 216 I posted earlier. Now when I click the SONARPLT.EXE file, I get this additional Windows error:

I then uninstalled the C++ Redist Update, and that didn't make anything better. Also now Command Center doesn't run. Unlike Sonar, it actually gets a PID and appears in Task Manager, but disappears after about 2 seconds. 
 
I'll reinstall the C++ redistributable and report back.
 

Downloaded the latest C++ redistributables from MS, and they installed. Command Center still loads momentarily and then drops from memory. Trying the Sonar stand-alone installer now...

OK so I installed Sonar with the standalone installer. It installed fine, no errors. Clicking OK with "launch the application" ticked gives me the error code 216:

If I then click the EXE after that, I get the blue Windows Compatibility warning. 
I tried running different compatibility settings and nothing worked. 
 
I looked up the error code 216, and found this recent post for a different application (no connection to Sonar):
https://github.com/Microsoft/vscode/issues/10592
where the last comment says try running the installer with the firewall off. I tried that, and now I have reverted to the original problem where Sonar gives no errors and just silently fails. 

Exciting development!  I uninstalled Sonar 64-bit and installed the 32 bit version. It installed fine, and actually ran! I get this single error about the start screen:

But otherwise I was able to get Sonar x86 to open projects and play them. (most plug ins were missing, but for what was there it worked fine). 
 
I don't know if anything I have posted rings any bells for anybody. Any additional help would be great. 
 
I am going to do a windows repair and see if that helps, otherwise I might have to bite the bullet and do a fresh install. 

I believe someone already mentioned rebooting your PC, but did you do it before you tried executing Sonar in safe mode?

If you open up task manager, you should only see one version of sonarplt.exe running. Sometimes when Sonar hangs, I've noticed that trying to run it again opens multiple processes, none of which will work. I usually kill all running instances and reboot.

The only recommendation I have left is to try that, and reboot your PC. Then execute Sonar in safe mode, as I described earlier (With the shift key). When asked (if you get that far), load the app with no plugins (There should be a dialog that allows you to cancel everything all at once). Aside from that and a hard drive issue, I've got nothing else. Running Sonar in 32 bit mode is not the answer, because without doubt Sonar 63B should run in a 64 B Windows 10 machine...

The reference I made to 32B was in reference to TTS-1, because it is a 32B plugin and it won't run using bitbridge on a 64 B machine, without changing the processor setting. Sorry for the confusion... I was replying to a different issue and posted the 32B thing in the wrong section.

You say you got 8meg so I am assuming you have Windows 10 Pro 64bit.  However, can you actually confirm that it's the 64bit version of windows installed.  Of course, if, it's the 32bit, then all you will see of that 8 gig is 4gig.

I've looked ahead at your progress and I must say, I have never experienced any of these (On my WIndows 7 ENT 64bit)

There is an issue with Dell backup software and newer version of SONAR 2016, see http://forum.cakewalk.com/FindPost/3474441

Musicman762
The reference I made to 32B was in reference to TTS-1, because it is a 32B plugin

This is not correct. TTS-1 is a DirectX plug-in and SONAR includes both 32 and 64bit versions. SONAR installs the appropriate 32 or 64bit version depending on the version on SONAR installed.

scook
There is an issue with Dell backup software and newer version of SONAR 2016, see http://forum.cakewalk.com/FindPost/3474441

Thanks, intriguing idea, but I built this system from scratch myself and didn't install most of the Dell bloatware. 

I don't know if any other programs mess with these overlays.

promidi
You say you got 8meg so I am assuming you have Windows 10 Pro 64bit.  However, can you actually confirm that it's the 64bit version of windows installed.  Of course, if, it's the 32bit, then all you will see of that 8 gig is 4gig.

I've looked ahead at your progress and I must say, I have never experienced any of these (On my WIndows 7 ENT 64bit)

Thanks yes, definitely running Windows 10 x64 on a 64-bit compatible machine =)