I am facing a special situation , actually I got some problmens with the ambari server which fails to start so I did :
Now when I access the 127.0.0.1:8080 I got a welcome page asking for the the creation of a cluster by launching the installation wizard . I don't egt the same view that I had the first tieme I used the sandbox
please see enclosed picture for the welcome page I get in Ambari
When I try to add hosts to cluster via ambari ( see the picture below) I got a fail message
Ambari Server stores the information about the cluster (and all it's config version details), Host informations ..etc inside it's Database
The ambari-server reset command will cause the Database to be cleaned up and reset to a state where only the DB schema exist and all the cluster details are wiped up.
You were not supposed to do the "ambari-server reset" , Because you did that hence the cluster information is lost.
If you have captured the Ambari Database dump before doing the "reset" then there was a possibility to import that Ambari DB dump back to the database and you could recover the cluster information.
Currently due to ambari-server reset the cluster information is lost and hence when you logged in to ambari UI it is giving you the option to create a new cluster.
As you are using Sandbox (and i assume you do not have the DB dump collected prior to ambari-server reset) So i will suggest you to Remove your Sandbox image and reimport it to your VirtualBox / VMWare to get the default Sandbox instance.