An UNAVALABLE Software Updates reads that there is no transponder available to update. Check that the transponder is power on and that the serial data is wired THAT display. If it is not wired to that display you need to disable the serial port function 74109 AF-XPDR-261 to allow the data to propagate from the other display. The other display would need to be configured properly.

Side Note 1: Please enter the Mode S Code for the aircraft of A9A7AD
Side Note 2: If you have the 74112 AF-ADSB-470 receiver you need to change the ADS-B In Frequency to UAT only.