Please follow this steps thoroughly, first, go to this link and download the
agency-home.zip file (that is the slider for the Agency demo that has been deleted on your site)
Then import that zip file to your Revolution Slider
Choose to Append on both options on Note: styles templates will be updated if they exist! dialog.
After you successfully imported the agency-home slider, navigate to your home page and edit it on Cornerstone.
Add a Classic Revolution Slider element on the first section of your home page (if you have not already)
On that Classic Revolution Slider's dropdown, select the Agency Home slider that you just Imported.
Save the page and view it on the frontend.
Hope it helps,