LM48580EVM: No audio output. Only 5V appears at Vbst

I have connected the LM48580 board to a 5V supply at VDD and to a line level audio source. At the Vbst touch point, I see only 5V, but I believe that I should be expecting ~20V. Is this an incorrect understanding on my part, or might there be a problem with the board.

Thanks.