no fuse, check the pins and also check program 109 and see if that slot got assigned for something other then an 8 port expansion card.
also check all your wiring off the amp connecter,
if there is a short on the data pair of any port it can knock out that whole card.
Also take the amp connector from the new extensions and plug it in to the good card and see if all the extensions work. This will check the new wiring.