Mysql DB Transfer White Screen

I have a customer that has come to me about his WordPress has been messing up. So I took a look at it. The code was clearly messed up, so I save page as’ and edited a page in dreamweaver to see what the code error was. Just to make sure that the DB was not messed up. It was not!

So then I assured him that by creating atleast 3 backups of his DB (only the posts, and comments and such. So he decided to have me do it for him.
I made 3 copies of the db and reinstalled wordpress on his account. Then went into the mysql admin and imported the .sql that I had backed up from the old site. (comments and posts)

Now when I visit the site
https://computer-desks-r-us.com/
there is nothing but a blank screen.

So I thought maybe he had plugins installed on his old DB so I checked that out and manually disable the only one there.
That still has not worked. The screen still is blank.

I have looked all over for a solution to this but really alls I am coming up with is disabling the plugins…

Does the config.php file have to match his old admin and user name for the old wordpress….
In general does everything on the new installation have to match the setting on the old DB backup.
I know that the config.php file has info in it to connect to the database but if that was incorrect it would say error making a connection to the database right?

IDK I know I am lost here. any help would be awesome