Could not log into ambari using user id "admin" and password "admin"

Can some one help? I am practicing using the sandbox but cannot log into ambari with url http://127.0.0.1:8080, and id “admin”/password “admin”. I did run “ambari-server start” and ambari-agent start”. The error I got is “http://127.0.0.1:8080 requires username and password. The server says XDB”