In Kalium and other WordPress themes, many issues you may run into such as white screen, demo content fails when importing, empty page content, changing skin problems and other similar issues are all related to low PHP configuration limits. The solution is to increase the PHP limits. You can do this on your own, or contact your web host and ask them to increase those limits to a minimum as follows:
Also consider upgrading your PHP version to the latest version, the newer the better.
How To Verify Your Current PHP Limits?
You can check your PHP configuration limits by installing the FastDev plugin and then going to WordPress dashboard > Fastdev > and choose the PHP tab to compare your server info (see example). The first column (Local) refers to your installation value, and the second column (Master) refers to the limits of your host. The latter values are often lower if you have selected a cheaper hosting package.
Updating your PHP version
In most cases you cannot update the PHP version yourself and need to contact your host about this. The upgrade process is an easy process and should be something your host can do for you without impacting your website or charging you a fee. Here’s a letter you can send to your hosting company:
I’m running a WordPress theme on one of your servers and WordPress and this theme has recommended using at least PHP 7 or greater. WordPress, the content management system that my theme uses, has listed PHP 7.4 as the recommended version on their requirements page: https://wordpress.org/about/requirements/
Can you please let me know if my hosting supports PHP 7.0 or greater and how I can upgrade?
Also please increase those limits to a minimum as follows:
Looking forward to your reply.