I got one as well but I am having some problems. I sent a support ticket to Amigakit. They came back with very vague information. I replied back to them and no response yet. I hope they can help me resolve it.
Mine is not seen by early startup and the crystal and main chip (FPGA?) get very warm. I asked about this behavior and they did not respond to that. I think it may have to do with my Mediator A4000D in a tower. Not sure. I hope they can look in to it more soon.
Are you having trouble with your Deneb, or with an internal 3.5" card reader? I am guessing it is your Deneb since you mention the FPGA chip getting warm and I don't think a card reader needs or has an FPGA chip.
IIRC, I read somewhere that the Deneb could be easily plugged in backwards which would ruin it and possibly damage your Amiga, but my memory might be faulty as it has been many months since the time when I think I read something like that. I hope that is not the case for your Deneb, good luck getting it working correctly.