If you are installing Avada in WordPress, but get a message that says Are you sure you want to do this?, the most likely reason is that your web server is configured with low PHP settings that only allow a certain size ZIP file to be uploaded via WP admin.
Most hosting companies configure their servers to only have the maximum file upload size limit at 8-10 MB; some are even less. The Avada ZIP file is currently about 8 MB in size. So, if you get this error, your web server is rejecting the upload due to the overall size of the Avada.zip file. WordPress is unfortunately giving you a rather ambiguous message in response. This is not an Avada issue or a bug.