I have done a test and the import data works fine. I don’t know what could be the problem. Could you create a new user for me in your admin panel? In that way, I can check the problem.
I have added the demo content and it works fine. The option ‘Import Demo Data’ from the page ‘Appearance > Import Demo Data’ didn’t work because there was a conflict with some plugin. I have deactivated the plugins and imported the content and it worked without problems.