Htaccess and index

Have you done this?

And this?

There’s no skill level required, the instructions are written so that you don’t have to familiarize yourself with the code of the software you’re running to be able to debug the issue.
More specifically, in WordPress, as the linked article mentions, you should go to the file manager and your website’s htdocs directory, find wp-config.php, and insert the following line in it:

// This enables debugging.
define( 'WP_DEBUG', true );

Making sure that this line has been inserted BEFORE this line (so not below it):

/* That's all, stop editing! Happy blogging. */