Thanks for updating the thread.
PHP version should not be an issue. As of today WordPress supports and recommends PHP 7.3 or greater. As there are multiple X Theme licences in your account, it's a bit difficult for me to test the website in question.
Can you please confirm that you are using latest version of X Theme and Cornerstone? As of today the latest version of X Theme and Cornerstone is 6.5.5 and 3.5.4 respectively.
Along with that, please share the website login details in secure note for us to take a closer look.