Thanks for writing in.
Please check first if your setup is updated to the latest version. You can check the link below for the latest versions.
how to update your setup:
You could also try to increase memory limit.
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. */
And also make sure that you have the following on your server configuration:
For more demo content troubleshooting and guidance, please check out the bottom aspect of the following page: https://theme.co/apex/forum/t/setup-demo-content/56
I hope this helps.
Let us know how it goes.