This is a pre-loader. It will disappear automatically when the browser complete the content loading. if it bother you then you can disabled it from elevation settings. There is a option for pre-loader on/off.
Thanks for the info! After much troubleshooting, I was able to disable the pre-loader option and manually install the demo content. However, the WordPress homepage is not full screen width for desktop even though I have gone to the homepage page and change the Page Attributes -> Template to Homepage. Is there anything that I am missing or can try?