L322 2006 l322 4.2 SC remote key work

Hi,
Can anyone help me with this issue please.
I have a 2006 rr sc that refuses to have a working remote .
I have changed batteries on both keys , even purchased new flip key and changed transponder over so key works fine manually but not as a remote fob.
I then changed the RF receiver and no different .
The central locking works perfectly with key and dash button.
I have resynced the keys so many times that my fingers bleed but nothing.
With the IID tool i get the fault B1BO1-87 KEY TRANSPONDER-BUS SIGNAL/MESSAGE FAILURE-MISSING A MESSAGE.
Anyone got a clue how to fix this please

Anyone got a clue how to sort this please

If you took the fobs a part did you make sure the little plastic cylinder up by the key end was still there as that is the transponder and is easyily lost.

HI, Thanks for reply
Yes the transponder is still there and the keys work in the ignition , its just the remote central locking which refuses to do anything