Thanks for using Hortonworks Data Platform.
Can you verify the the namenode is indeed running by executing the following command?
If the NameNode is running there should be 'NameNode' listed.
On another note: It is best to avoid using the 'start-all.sh' script to start the hadoop services on an HDP installation, it will start the services as the 'root' user and change the permissions on several directories to be owned by root. The best way to start the hadoop services manually is with the 'hadoop-daemon.sh' script like this:
su - -c '/usr/lib/hadoop/bin/hadoop-daemon.sh --config /etc/hadoop/conf start'
where 'hadoop-user' is either 'hdfs' or 'mapred' depending on which of the hadoop daemons you are launching: namenode and datanodes use hdfs, jobtracker and tasktrackers use mapred.
But overall on a system that it install using Ambari it is ultimately best to start all of the service through the Ambari UI as that will use the proper user for each service. At this point since you did use 'start-all.sh' you will need to find the directories that have been changed to the incorrect owner and chown them back the the correct owner.