navnet vx2 1720C/NT software update



I bought a used Cabo 32 with two 10.4 navnet vx2 at the helm that work wonderfully. They have always been kept up to date. There is a 1720C/NT in the tower that has ver 1.04 software. According to other posts on this forum the software will have to be updated in a step wise fashion. I have tried to update with an SD card from the furuno dealer to 4.03 tday and the machine will not recognize the card. I understand the next step is to get 1.06. Does anyone know where I can download this version and any subsequent versions I will need to bring the insturment up to date.
many thanks for any help
thank you furuno customer service
they just sent me the software. Pretty fast response. I guess I am the impatient type.