Hello,
Please deactivate all the third-party plugins and activate only theme-required plugins on the site and then check the issue. I am sure your issue will be solved. Then, activate the third-party plugins one by one and check which plugin is creating the issue for you.
If the issue remains, try to increase the “PHP Max Input Vars” parameter to 10000 or higher in your PHP configuration and import the demo again.
Otherwise, if the issue still exists, then keep the third-party plugins deactivated and share the WP logins details so I can check and give you a possible solution.
Best Regards,