I have tried to get the Demo Sites to appear, and I can’t do it for my site hosted on WPEngine.
I checked the following settings and they seem to be good:
allow_url_fopen = On
upload_max_filesize = 512M
post_max_size = 512M
max_execution_time = 300
max_input_time = 300
max_allowed_packet = 16Mb
innodb_log_file_size = 128mb
Is there some type of problem on your end?