There is a known issue on some installations of Yellowfin 7.3
This issues however is easily resolved:
Using the administrator command prompt - navigate to [yellowfin]/appserver/bin
1. remove the yellowfin service.
service remove yellowfin
2. re-add the service
service install yellowfin
3. start the service
service start yellowfin
once started, you can confirm if the service is running by checking
if this page returns, try logging in
This issue is due to security changes within Windows - we hope to have this resolved in a future Yellowfin version.