After upgrading to Snow License Manager (SLM) 9.16.1 you may see this error message when trying to access it:

"Server Error in '/' Application.

Runtime Error

Description: An exception occurred while processing your request. Additionally, another exception occurred while executing the custom error page for the first exception. The request has been terminated."

The upgrade to 9.16.1 may not have completed correctly and so as a workaround we can try applying the upgrade again.  To do so:
 

• Open up the windows registry by using the regedit command.
• Within the registry navigate to HKEY_LOCAL_MACHINE > SOFTWARE > SNOW SOFTWARE > SNOW UPDATE SERVICE > INSTALLED PRODUCTS > SNOWLICENSEMANAGERENTERPRISEEDITION - This presents the following page:

• In the following values make changes,
  • DataBaseVersion - Change from 9.16.01 to 9.16.00
  • ProductVersion - Change from 9.16.01 to 9.16.00
  • UpdateRevision - Change from 490 to 489

• Save the changes and start up the Snow Update Service.
• This should carry out the necessary checks and show 9.16.1 as being available to reapply.

We believe that this may be caused by files that are in use during the upgrade to 9.16.1. The upgrade incorrectly completes successfully when in it hasn't completed all the upgrade steps.