After a lengthy but successful download of Omni 2 I ran the installer.  Everything went swimmingly until about halfway through the install when it hung up for about 2 hours ( I just let it run while I was in sessions).  Wouldn't cancel.  Had to do a Ctrl-Alt-Del to get back to the desktop.  Tried to re-install the upgrade...error dialogues galore...no love.  Opened Sonar to see if Omni 1 would still work.  Got Windows Defender warnings on Omni scan...ignored them...I live on the edge.  Tried to open Omni 1 and got another Windows Defender warning...ignored it too...fools rush in where angels fear to tread.  Omni 1 wouldn't open and crashed Sonar & the DAW.  Had to force a shut down.  Then the DAW would not power back up until I disconnected the external SSD drive where all my Spectrasonics stuff is.  Finally got back up and running.  Tried to re-install Omni 2...error dialogues galore.  Opened Sonar back up...no warnings.  Tried to open Omni 1.  This time the Omni 2 authorization splash screen came up.  
 
So...Omni 1 does not work and Sonar thinks Omni 2 is installed even though it's not, and Omni 2 will not install.
 
Have left two different phone messages and now 2 different emails at Spectrasonics.
 
Now listening to the sound of crickets and a dry wind.
 
Current position:  fetal
Current state: sucking thumb and crying
 
Sigh....

Man, that sucks. Spectrasonics makes great products but their support has often been criticized. Have you tried a complete uninstall-reinstall? I'm thinking either the download was corrupt or Windows Defender is interfering with the installer (never seen the latter happen, though). 
 
Check if the executable got installed (here it's c:\program files\cakewalk\vstplugins\omnisphere.dll, ver. 2.2.0 and dated 8/21/18). Wherever the STEAM folder is, there should be a subdirectory named Omnisphere, with a sh*tload of files (3,086 files in 1,673 directories, ~64GB).
 
 

I commiserate with you yoropal. I have been sitting on Omni 1 since 2005 or wheneverthehades it came out. I was tempted to upgrade but never could justify what I thought was a prohibitive cost. I really hope yours works out. What were you seeing in Omni 2 or hoping to get out of it?
 
Is it a STEAM folder thing? Lord help you if you move the STEAM folder or install elsewhere. Does Omni2 create a different STEAM folder?
 
I can see why you are STEAMED. good luck bro

I'm assuming that you tried to install Omnisphere 2.5 (as it's the current version now) over Omnisphere 1.0.  It's possible that you needed to go to 2.0 from 1.0, then on to 2.5.

I don't think it's necessary to install intermediate revisions. 2.5 should go in fine whether you're currently at 1.x or 2.0.
 
emeraldsoul's right - most of Spectrasonics install problems have something to do with where the STEAM folder is located. In my case, I have a dummy folder on drive D: (where Omnisphere 1 was originally installed) that contains a symbolic link to the actual location (e:\libs\spectrasonics\STEAM). Once I put that scheme into place, subsequent updates have known exactly where to go.
 
However, YoP's symptoms suggest that something else has gone wrong. Either the installation file is corrupt or local security policies are interfering with proper installation.

Welp...the fellers at Spectrasonics finally got back to me and have sent me both a new set of download manager/files and Brian is going to call me on Monday and we'll walk through the troubleshooting together.  I'll keep ya posted.  I'm guessing it was just a corrupted download.  But I'll know more on Monday.