If it had been working and has stopped, it may be an issue with your database server, so try contacting your host about that.
Otherwise, there are only 4 fields
user
password
host
db name
One or more of them is wrong. Verify them with the settings you used when you created the database.
This script helps nail down which one
https://gist.github.com/sivel/162913
// update
trying to access your site, I get
Service Temporarily Unavailable
The server closed the connection without sending any data.
The server is temporarily unable to service your request due to maintenance downtime or capacity problems.
Due to heavy load on the server, connections may be temporarily blocked from locations that fetch an unusually high number of pages.
——————-
Definitely looks like a hosting issue to me
