1.You can look in your ftp root folder for a folder called logs.
2.You can enable Debug
https://doc.osclass.org/Debug_PHP_errorsYou can put this
/**
* Copy this code to config.php file
* This will log all error notices and warnings to a file called debug.log in oc-content
*/
define('OSC_DEBUG', true) ;
define('OSC_DEBUG_LOG', true) ;
in your config.php file.
In oc-content is the place to put an empty file called debug.log with 666 permissions.
The first choice has already the errors, if any,
The second will be populated with them from now on if you hadn't enabled it so far.
Edit:
Regarding changing your password from phpMyAdmin, you can do it, but you must find out what hash is used by osclass for storing pw.(I never done it in osclass, but I've done it in WP).