AIN-EF config over modbus

Hello.  I am not an experianced user.  A few years ago, I programmed a universal windows application as a mod bus client (running on a Rasperry pi).  It worked fine.  I have got my Labjack out of the shed again for another applicatin and am re-cycling the code (yes their may be libraries avaliable now but the existing solution is 99% fine).

My problem: when I write a value to register 9004 i can write fine..  Same code for 9304, it doesnt matter what i write - it always reverts to 0, even if it was already 1.  I must be missing something....

I hope someone else can quickly spot my problem!

Thanks & regards

nmo

byte[] response = new byte[20];
            byte[] write = { 0x00, 0x04, 0x00, 0x00, 0x00, 0x0B, 0x01, 0x10, 0x00, 0x00, 0x00, 0x02, 0x04, 0x00, 0x00, 0x00, 0x00 };
            
            ushort address = 9304; //
            byte[] byteArray = GetHexAddress(address);   
            write[8] = byteArray[0];//set the address
            write[9] = byteArray[1];//set the address
            write[16] = 0x01; // set 01 (0x01) to enable configA bu not working - always reverts to 0
            server.Send(write); //set this 
            server.Receive(response);
                
            address = 9004; //9002 is input 2 extended function index - set to 1 for K type thermocouple
            byteArray = GetHexAddress(address);
            write[8] = byteArray[0];//set the address
            write[9] = byteArray[1];//set the address
            write[16] = 0x16; // set 22 (0x16) to enable type k
            server.Send(write); //set this 
            server.Receive(response);