Based n your recent screenshot looks like the boot operation is completed successfully (Even though you do not see the welcome message of Sandbox in the mentioned screenshot). So i guess you should be able to access the ambari UI as well as the SSH session to the sandbox without any issue.
So can you please try this:
1. Login to Sandbox using SSH on port 2222 as following:
# ssh firstname.lastname@example.org -p 2222
Enter Password: hadoop
2. You can also try accessing the web terminal: http://localhost:4200
3. Also please try accessing ambari UI to see if it works. http://localhost:8080