first connection attempt failed with MongoParseError: URI does not have hostname, domain name and tld code example

Example: UnhandledPromiseRejectionWarning: MongoParseError: URI does not have hostname, domain name and tld

Ensure special characters in your password are encoded. 
For example if your password contains '#' you should replace the literal '#' character with '%23' where 23 is the hex code for '#' 
see: https://docs.atlas.mongodb.com/troubleshoot-connection/#special-characters-in-connection-string-password