I imagine this will go smoothly, but it seems the download within Waves Central is huge...just to add this and the free Tap Delay to my Waves plugin collections.  It will take about 6 hours as Waves has divided the download into 32 sections, and my download speed is a mere 1.7mb/s.  You can see all the sections if you look at "processes" in the Task Manager.  Crazy?
 
You know what else is weird?  On my Studio A computer, Waves Central shows I have no Waves plugins installed, which is fine because I transferred them all to the Studio B computer.  But...the plugins are all still in Sonar Plat - in Studio A, and can be inserted into projects just fine.  So they are on BOTH computers.  Odd...
 
I swore I wouldn't mess with Waves anymore, because it just makes me nervous, but I got that Vinyl Plug for $69 over Black Friday, if only just for the kick asp graphics...I hope I don't regret my impulsiveness...anyway will post back here in 6 hours if the install on Studio B and the Sonar scan goes well and lists the two new plugins. 

I don't think the download is that big (probably depends on when you updated last using WAVES central), however, download speed can be quite slow (at the other end) because despite having a quick connection here, installing AR vinyl plus a few others took quite some time here as well.
 
whether or not plugs are shown/removed from Sonar depends on your VST scan settings (manual, on start-up, auto) ...

Update:  Downloads failed.  ROFL!  Don't have time to monkey with this now.  Will try again some other time.

Seems like you have a great spec on your machine.  I don't know why you have such an issue with downloading anything from Waves.  It takes a very short time. Their process works very smoothly.   Maybe you have a dicey Internet connection?

The last time I installed a Waves plugin was 2014.  It seems that Waves wants to download the entire Wave
Shell all over again, possibly because the the entire suite has been updated since then?  That's 1+ gb I think.  After 6 hours it got halfway downloaded and then stopped at "done sync".  The next couple of times it just threw an error after a few minutes.  Rebooting did not improve things.  There is a page at Waves which says what to do when this occurs, and it involves deleting all Waves folders and files, caches, etc, and starting over.  That's too scary for me right now...Everything works as is...and I smell trouble:
 
This is for installation problems, not downloading problems, so not sure if any of it applies to me yet, but wow...what a nightmare if it does:
http://www.waves.com/supp...on-using-waves-central

I find the best way to deal with Waves is to follow their instructions exactly and avoid custom D/L locations. The good news is that their support is excellent and you have new stuff to install, so no WUP issues. Contact them, the shell should only take a couple minutes to D/L. 
Over the weekend and into cyber Monday there was a huge internet load and at least one denial of service attack in Europe. We felt the effect here on the forums and Waves is in Israel, so it may have had an impact.

What John said. Even thought I have a custom VST folder for almost everything, Waves and UAD I always let install in their default locations and I have far fewer problems. I tried a custom location for Waves and things went to hell. I followed the instructions to fully scrub Waves, installed into the default location, and haven't had a problem yet.
 
I often buy new Waves plugins and try demos, so I run the installer a lot and it is pretty solid for me.

Well I tried again and the two new plugs downloaded, installed, and activated in about 3 minutes, and Sonar picked up the plugs in the auto scan and were there and functioning within Sonar.
 
The only problem is all my other Waves plugins were gone from Sonar. 
 
I moved all the licenses back to the cloud and am trying to download and install all of them at once this time (old and new) and am getting that very very long download wait time again...32 processes in parallel instead of just one...
 
Not a scintilla of blue on the progress bar...but lots of action on the 32 cURL executables in Task Manager.
Gonna wait this one out for now...
 
...and it's gone!  Failed that is.
 
I did notice that all my old WaveShellVST9.3 files have been replaced with new 9.6 files.  That explains the missing old plugins...now to figure out how to put all the old plugins back in the new 9.6 shells.

If you get stuck I can personally vouch for their phone tech support. Just top notch, and they won't give up till you're happy.

Moving from 9.3 to 9.6 shouldn't have caused you to lose the previously installed files. Is it possible that you had installed to a different location before? Have you tried to do a full wipe of Waves and then install?