Beverly,
Is the snort database and snortd process running on the same box?
If yes
Check the log to make sure Barnyard2 started successfully. Is it running?
Does the db user have appropriate permissions to connect from localhost?
Check the database logs for failed logins.
If No:
Make sure barnyard2 is running with appropriate command line flags set.
Does the db user have appropriate permissions to connect to the database from the sensor?
For example if you had a DB user called snort created in MySQL. The DB user [snort] should be able to connect to the snort database from any IP or a single IP.
Check DB logs for failed logins.
90% of the time if there there is unified2 files and barnyard2 is running and there is no data in the database, it is because the DB user does not have permissions to connect and insert the data into the database.
Good luck
John Kennedy