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 <> '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 <> 'master'
BEGIN
SET @CurrentBackupType = 'DIFF'
END
IF @CurrentBackupType = 'DIFF' AND (@CurrentDatabaseName = 'master' OR @CurrentDifferentialBaseLSN IS NULL OR (@CurrentModifiedExtentPageCount * 1. / @CurrentAllocatedExtentPageCount * 100 >= @ModificationLevel))
BEGIN
SET @CurrentBackupType = 'FULL'
END
END