Unable to connect to database. Check database connection information and make sure the database server is running. The user has proper permissions. No other user is experiencing this issue. The user can access the rest of the site properly.
The database is up, everything is connected. No other user is reporting this issue on any other site or list, but that Other users can access this list.
Problem: I have to be honest, I am not entirely sure what the underlaying issue was. I only know that the site owners had taken out all of the out-of-the-box SharePoint default security groups. They deleted the site owners, viewers and members.
I put back the default groups on the site and everything worked again. The error message disappeared and the user was able to access the list without a problem. All of the research I did about these groups mentioned that you should be able to remove all of these groups without an issue, but this was not my experience.