Can you try adding the code below in your
wp-config.php file located at the root directory of your site.
define( 'WP_MEMORY_LIMIT', '256M' );
define( 'WP_MAX_MEMORY_LIMIT', '512M' );
You may add it before this line
/* That's all, stop editing! Happy blogging. */
If that doesn't help, kindly provide us your wordpress & ftp login in