Ola Hallengren MaintenanceSolution - Differential - the value for @ModificationLevel is not supported
This indicates that you are hitting the validation (taken from Ola Hallengren's site here)

  IF @ModificationLevel IS NOT NULL AND NOT EXISTS(SELECT * FROM sys.all_columns WHERE object_id = OBJECT_ID('sys.dm_db_file_space_usage') AND name = 'modified_extent_page_count')
  BEGIN
    INSERT INTO @Errors ([Message], Severity, [State])
    SELECT 'The value for the parameter @ModificationLevel is not supported.', 16, 1
  END

  IF @ModificationLevel IS NOT NULL AND @ChangeBackupType = 'N'
  BEGIN
    INSERT INTO @Errors ([Message], Severity, [State])
    SELECT 'The value for the parameter @ModificationLevel is not supported.', 16, 2
  END

  IF @ModificationLevel IS NOT NULL AND @BackupType &lt;&gt; 'DIFF'
  BEGIN
    INSERT INTO @Errors ([Message], Severity, [State])
    SELECT 'The value for the parameter @ModificationLevel is not supported.', 16, 3
  END


Please check the conditions and also keep in mind the @ModificationLevel is the difference needed for a Full backup to occur. If there is not enough difference it won't do the Full backup.

IF @ChangeBackupType = 'Y'
    BEGIN
      IF @CurrentBackupType = 'LOG' AND @CurrentRecoveryModel IN('FULL','BULK_LOGGED') AND @CurrentLogLSN IS NULL AND @CurrentDatabaseName &lt;&gt; 'master'
      BEGIN
        SET @CurrentBackupType = 'DIFF'
      END
      IF @CurrentBackupType = 'DIFF' AND (@CurrentDatabaseName = 'master' OR @CurrentDifferentialBaseLSN IS NULL OR (@CurrentModifiedExtentPageCount * 1. / @CurrentAllocatedExtentPageCount * 100 &gt;= @ModificationLevel))
      BEGIN
        SET @CurrentBackupType = 'FULL'
      END
    END