Have you been waiting for several minutes and the site taking too much time to import demo data?
If the import stalls and fails to respond after a few minutes, then it’s likely that your PHP configuration limits are set too low to complete the process. You should contact your hosting provider and ask them to increase those limits to a minimum as follows:
max_execution_time 3000 memory_limit 512M post_max_size 256M upload_max_filesize 256M
