What is your store domain?
You can create a support ticket here: https://treedify.freshdesk.com/support/tickets/new
You could also try to set this kind of a discount with Bundler - Product Bundles. It allows you to set a discount on selected products and set a minimum and maximum requirement.
So in your case, you would create a new bundle, select the products you want to have in the bundle and set the minimum and maximum requirement to 3. This means that every time a customer purchases 3 of the selected products (any combination), the app will set a discount on his order :)
If you decide to try it out and need any kind of help, just send us an email :)
This app will provide you bundle for the products you selected and wall offer discount on these bundles.