Hmm it sounds DOA to me. What’s annoying though is that we hand programmer t5577 chips ourselves so we know they are good when they leave… but that’s not always a guarantee.
Since you are not getting any coupling with LF tune… it seems dead… but could you confirm you are placing the ring LF side down on the LF antenna and trying a few different positions including centered but also overtop the enamel wire of the LF antenna and still getting no change?