Last night I bought Sunset Studio Reverb. Opened PM which immediately notified me that Soundest has been successfully registered. But it was not listed in the My Products list.
Story (scroll down if you only want to see the - simple - solution):
This is on Windows 10.
I Went to the My Products page of the IK website. No installer. "Get Product Manager" instead.
So I downloaded the Product Manager Installer to realize that the one I already had was up to date.
Re-installed it anyway. Still did not show any Sunset.
Then I realized that my copy of the T-RackS program is waiting for an update (PLEASE note this is not a feature request! I love that IK does not force nor nag me to keep my stuff up to date, since my WLAN is connected via USB and thus shares traffic with my audio card).
I thought that won't harm me and clicked the Update button. PM froze for a few seconds and, after awaking again, nothing happened.
Restarted my computer.
Same behaviour afterwards.
I tried to resort to the Custom Shop. Found Sunset with a "Try" button. Oh cool, thought I, this might get me a demo copy which I can autorize then. Wrong. After I clicked "Try", CS realized that Sunset is already registered and did nothing further.
I returned to PM and radomly clicked around in it. I opened a Settings window and found a typo in my download path. Tried to correct it. The text field with the path in it was read-only. Clicked the Browse button. No reaction. I posted a feature wish, "please let me correct my download path".
I created a folder with the same typo in its name. Now the Browse button started working.
As a test, I updated T-RackS.
And here is where the solution comes in:
SOLUTION
1. Make sure PM can access the Downloads folder. If it is on an external disk, make sure it is properly connected. If you can't change the Path in PM, create the corresponding folder and make sure it is writable.
2. If your new PlugIn belongs to a particular App/Suite/whatever you name it (such as T-RackS or Amplitube), make sure your app is up to date. In my case, the most recent version of T-RackS came with ALL plugins (even the un-registered ones), and there seemed to be no way (and no further necessity) to install individual plugins.