Discovery's MSSql DB On Windows Pattern is not able to create MSFT SQL Instance CIs if the instance name contains an underscore "_" (underline, low line, low dash)
The "MSSQL populate database table" pattern library step 2 "Set parameter for Condition two - list db from wmi" is responsible.
This problem has been fixed. If you are able to upgrade, review the Fixed In or Intended Fix Version fields to determine whether any versions have a planned or permanent fix.
The fix in Rome was to add fail over steps to remove '_' from instance name in case if the dbs are not discovered, update set attached