Hello,
Thanks for contacting us.
Sometimes when you import demo with a great number of the images the server timeout is not enough to import all the media that demo has and this error occurred. You can choose the demo import again and at the demo content installation step don’t check all but media only, for example, https://gyazo.com/647b0452f7c5d8ddb3ebcf966506dcc0 , or do a manual import of the media (Tools > Import > WordPress > using the media file from the Import files folder).
Let us know if you need any further assistance.
Regards















