Hi There,
Thanks for asking.
Please try increasing memory limit. You can do this by editing your wp-config.php file which can be located under the root of your WordPress installation. Upon increasing the memory please try again and see how it goes.
Add the following lines into that file.
define( 'WP_MEMORY_LIMIT', '512M' );
define( 'WP_MAX_MEMORY_LIMIT', '512M' );
You can add it before the line
/*That's all, stop editing! Happy Blogging. */
Also please make sure that you are using supported version of PHP 5.6 (minimum) and Mysql. You can take a look at following article to for more information. https://wordpress.org/about/requirements/
In case problem is still there, please share login details using secure note feature for us to take a closer look.
Thanks.