6
I just got this same issue fixed on my site.
It had been installed and working just fine for several months. Then, suddenly, nothing.
It turns out my hosting provider had done something on the server that houses my database, and it was denying access to my username & password.
So it was also denying access to the XOOPS script running my site when it tried to access the database using that username & password.
Once they fixed the permissions problem, the site "magically" appeared once again.