DB doesn't connect

Hi!

first of all, thanks for your valuable help!

I’ll explain you my problem:
I moved a website (php + backoffice) to a new host, but the same server company (Cdmon). Once I copied the files and imported the DB, it’s time to write the name in the address bar and check the website.

Everything seems work right, until I click on a link and … [COLOR=“red”]Error 404[/COLOR]! It seems that the query doesn’t find results. However, the DB (data and structure) is there …

More clues …

When I try to enter into the backoffice, I can’t see the login screen, and this message appears:
[COLOR=“Red”]Unable to connect to your database server using the setting Provided[/COLOR]

I have checked username / password and they are correct.

Would you like to help me?

Thanks a lot!!