Failed to connect to configuration database error.

You may have encountered this problem when you want to add a new server ( e.g web front end ) to your existing sharepoint server farm. During  step 2 of configuring server – connecting to configuration database – , it fails and sharepoint gives you this error : 
Failed to connect to the configuration database.

To be honest I don’t know the exact way to solve this issue. but I recommend you doing some checks :

• Check the version and service pack of each sharepoint. both should be the same. for example both server should have SP1.
• Check that your databases can see each other !! you’d better to have some database Roles. at least dbcreator,security admin, and sysadmin.
• Be careful : updatefarmcredentials & updateaccountpassword are different !  UpdateFarmCredentials Updates the Web application pool for the SharePoint Central Administration Web site and the Windows SharePoint Services Timer service (SPTimer). but Updateaccountpassword Updates the Web application pool passwords.
• On the server with central administration you should use UpdateFarmCredentials. If the problem persists use -local with UpdateFarmCredentials. and then iisreset /noforce .
• On the front end server use UpdateAccountPassword.

I myself use this way and it solved my problem. may be this way is your way to solve this issue. good luck 🙂