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Thanks for writing in!
Please ensure that the WordPress dashboard url is using the same http or https protocol with the Site URL and WordPress Address URL in settings, Settings > General.
In most cases, a loading screen could mean a PHP memory exhaustion. We recommend that you increase your memory allocated to PHP. To increase it, please edit your wp-config.php file and insert these lines:
define( 'WP_MEMORY_LIMIT', '256M' );
define( 'WP_MAX_MEMORY_LIMIT', '512M' );
You can add it before the line
/*That's all, stop editing! Happy Blogging. */
We would loved to know if this has work for you. Thank you.