My didn’t receive my order yet

Description

Hello, So I received a message that the case I had with a seller is closed (I previously opened a case that my order didn’t arrive) because they provided with a tracking number for my order. The problem is that I do have the tracking number, but I know no courier name to check with that tracking number to see where my order is! I placed it in December already and I have no package received so far! The merchant doesn’t respond and I don’t know what to do. What can I do? Thank you for your answer!