• After an upgrade users were are unable to access Snow License Manager (SLM) webpage. 
• The error 'Server Error in '/' Application - CS0016 Compilation Error' was displayed. 

• The source error [No Relevant Source Lines] was present in the body of the error.

• Snow License Manager (SLM) - 9.8.0
• Snow Inventory Server (SIS) - 6.4.0

Reproduction Steps:

• Upgrade to SLM 9.8.0 on a test environment.
• Open Snow License Manager Web Portal.
• Check if you receive the above error.
• If not:
  • Navigate to the directory C:\Windows\Microsoft.NET\Framework64\v4.0.30319
  • Right Click on the folder > Properties > Security
  • Check if the relevant permissions have been applied. The NETWORK account for this example did not have the appropriate permissions. (Consult with the customers internal IT team on level of security applied – i.e. Local Service or Network Service).
  • Remove Network Service permissions from C:\Windows\Microsoft.NET\Framework64\v4.0.30319
  • Remove Network permissions from C:\Windows\Temp
  • Restart Snow License Manager (SLM) services
  • Navigate to IIS & Recycle Application Pools
  • Open Snow License Manager Web Portal & you should receive a similar error to the above.

• Determined that the error related to Network Service not having correct permissions to the folder C:\Windows\Microsoft.NET\Framework64\v4.0.30319 in the error message.
• .NET framework may have corrupted when they were upgrading (possibly a lock on the file) when the upgrade happened.
  • C:\Windows\Microsoft.NET\Framework64\v4.0.30319
  • C:\Windows\Temp
• After checking with the IT team they were able to add Network Service access with the required security applied (i.e. Local Service or Network Service)
• Next they flushed out the application pools within IIS..

• They then restarted the IIS service by opening command prompt (Run As Administrator) & typing “IISRESET” & Enter.

• During upgrade it is believed that a corruption to .NET Framework caused the file processing to be unable to write files to C:\Windows\Temp.
• Adding the Network Service user access to the C:\Windows\Microsoft.NET\Framework64\v4.0.30319 folder & C:\Windows\Temp; flushing out the application pools & restarting the IIS service resolved the issue in this instance.