Running late item

Hello, I am a buyer of a specific item I ordered on amazon I bought a huge and heavy package. I waited for it to come. It stated It was going to come aug 4. Never came. So It wasn’t going to be shipped directly from amazon it was getting shipped from fedex. But theres a problem Fedex had put that they delivered my package and I still have not received. Now on amazon it says running late but it says to contact seller for the refund. Do I have to contact seller or should I just wait my refund to come automatically. Im not sure im new to this amazon stuff so im not so sure. Any piece of advice will help thanks!