Android NFCAdapter - Issue with AuthenticateSectorWithKeyA

Developing Android App in .net Maui. Having issues with NFCAdapter, specifically passing a specific sector key with AuthenticateSectorWithKeyA.
We print and encode our own Mifare 1K cards. Print software allows us to change the sector key A. I have tried multiple, and all ok, but need a specific key to work which is failing authentication.

No problem passing the following Keys and authenticating the sector with AuthenticateSectorWithKeyA.


byte[] keybytes = new byte[] { (byte)0xff, (byte)0xff, (byte)0xff, (byte)0xff, (byte)0xff, (byte)0xff };

OR
byte[] keybytes = new byte[] { (byte)0xAB, (byte)0xCD, (byte)0xEF, (byte)0x12, (byte)0x34, (byte)0x56 };

var auth = tag.AuthenticateSectorWithKeyA(0, keybytes);

All ok, var auth = true

But when I try the following Key it fails to authenticate. var auth = false.

byte[] keybytes = new byte[] { (byte)0x19, (byte)0x23, (byte)0x86, (byte)0x18, (byte)0x05, (byte)0x00 };

HEXString is 192386180500

Only thing I can see if the last two bytes have a zero prefix

SO
Tried:

byte[] keybytes = new byte[] { (byte)0xAB, (byte)0xCD, (byte)0xEF, (byte)0x12, (byte)0x34, (byte)0x56 };
Result: OK - var auth = True

Tried:

byte[] keybytes = new byte[] { (byte)0x19, (byte)0x23, (byte)0x86, (byte)0x18, (byte)0x05, (byte)0x00 };

Result: Fail - var auth = false

Use this key with non android RFID readers and all is ok. Need to use this key as we have produced thousands of RFID cards with this key A for sector 0.

Bit new to Hex and byte arrays, any help welcome.