Buy $30, get a gift

Hello, I am trying to add a product to the cart automatically for orders over $30. No matter what I do, it will not work, and if I type the code in it says it is invalid. Can you give us some pointers? Thanks

Hello,

Can you give details of how you set up the coupon code?

I just posted a similar answer here:
https://awodev.com/blog/buy-x-get-y-joomla-guide#comment-5783