AOA had been working fine but one day I noticed there was no aural indication when landing. The display was fine, but there was no beeping. I was thinking that perhaps I was landing fast, but I tried a full stall landing and there was no aural AOA indication. I tested it in flight and confirmed the display was working accurately but there was no tone, even for a full stall. I did a recal and afterwards I did get the tone but, upon landing and on my next flight when I did a full stall, there were no tones. I upgraded to Ver 14 and and again did a recal, but afterwards there is still no tone. In setup, the AOA volume is set for 100%, it is set to start in the mid-yellow region, and is set to be active above 35 kts. Any ideas?