I had the same "Could not connect to the database server" issue and it was driving me crazy. In the final solution, it turned out to be a simple problem.

My hosting provider uses cPanel, which has its own routine for creating MySQL databases, and that is what I used.

Let's assume my provider account is named GORILLA and I create a MySQL database named XOOPS1 and a db user named XOOPSER. The "official" names of the database and user become GORILLA_XOOPS1 and GORILLA_XOOPSER, respectively.

Using GORILLA_XOOPS1 and GORILLA_XOOPSER for the names in my XOOPS setup (instead of simply XOOPS1 and XOOPSER) solved the problem!

Xoops setup "Could not connect to the database server" because I had been giving it the wrong names.

Such is life in the Jungle.

ya ptefix_db and prefix_user must be defined.

In most cases I would not reccomend allowing a cms to create your satabases for you. Always create and define them yourself.

Prefix_user
Pass
Prefix_db

in the installer you have to define it at the bottom, this is seperate from your db prefix's.

Also be sure to use custom table prefixes. What I mean is do not use the default xoops_ table prefix.