how can I connect to a remote mongo server from Mac OS terminal
May be You are connecting fine but don’t have sufficient privileges to run show dbs.
You don’t want to execute the db.auth if you pass the auth in the command line:
mongo somewhere.mongolayer.com:10011/my_database -u username -p password
you able to see the collections for, when your connect
> show collections
If so all is good and you don’t have admin prerogative to the database and can’t execute the show dbs