I've checked the similar posts, but there were no published solutions about the matter.
When I visit the site (url https://www.ganasport.it) the unite revolution slider 2 (4.7.1) turns to grey in any "image backgrounded" slide.
Not the same in the http version.
Please is there any solution?
edit your slider and under the "Import / Export" section use "Replace Image Url's" to change image URLs
I used DB replacer from Regular Labs to change all my urls from http to https
Hope it helps
OK if it works for you