Why are posts and pages missing after importing demo data?

Question

WordPress

I used the Pennews theme many times, once again I wanted to take it for a new site, but after importing the demo data from the theme template, the site does not have any posts, pages, or a slider in the header, which are on the demo page of the theme template. At the same time, no error messages appear during the import, and the developers themselves claim that everything is in order with the template. If someone has the opportunity, please check this template for yourself and suggest how to solve this problem.