I've been using Omnisphere for a couple of years, together with Sonar X1, with no problems at all.
Just now I opened a Sonar file which contained some Omnisphere tracks. The Omnisphere tracks didn't give any sound (previously they worked fine). I checked the Insert-Soft synth command (in Sonar) and Omnisphere was not on the list of available instruments (previously it had been).
I have not made (knowingly) any changes to set up - what could of happened, and how can I get Omnisphere back?