Zen Cart v1.5.6c
TIP: More information may be available by clicking on the titles of some errors and warnings.
An existing configure.php file was found. The installer will attempt to upgrade your database structure if you choose "Upgrade..." below.
Some problems that need fixing before we continue
Problems with database connection based on the entries in your current configure.php
1045:Access denied for user 'arachni_user'@'localhost' (using password: YES)
Some Other Issues:
The GZip Extension in PHP is not enabled
This may not be relevant if you are using Nginx and handling GZip within Nginx.