When using MongoHQ sandbox plans and logging in from the console, there are a couple of things that are at play:
- When you connected, using the string above, you are already in your database (tnh_data)
- You do not have admin-level access, so "show dbs" will not work in MongoDB console.
So, in MongoDB console, connect again using the same string you started with and, once connected, run this command: "show collections".
Also, without trying to switch to another database, run your insert again. It should work normally this time.
Hope this information is helpful!