回複：Help!在線等。。綠卡已經收到了，還需要再去按手印麽？？謝！

I experienced exactly the same.

I called USCIS and the officer told me that I had to show up in the Support Center and the officer there would tell me whether to have biometrics taken or not.

Two days later, I called again and spoke to a different officer. And she told me ignore the biometirc appointment. So I returned the biometrics appointment letter along with a letter stating the situation and the officer's ID and her instruction.

I have heard nothing from them ever since.

Good luck.