G'day jwb1981, welcome to Noeman.
I guess you have an earlier model Subi [pre MY08 at least] as the later models use the C2 disc.
Provided you have the original disc supplied with the car when new [the OEM DVD], you maybe should try to 'wipe' the software from the unit's volatile memory by disconnecting the power to it overnight. Please note that disconnecting the battery can sometimes result in being able to start the car without dealer intervention with some Subaru models, so it would be better to just disconnect the unit itself only. When you power it up again, it should then prompt you for the OEM disc which contains the essential software. Make sure you eject the current map disc before you try that, and don't try it at all unless you definitely have the OEM disc.
Then again, the fact that there's NO sound at all, even radio or aux may indicate that it's nothing to do with the GPS firmware and you have some co-incidental generic problem with the sound which is unrelated to the V19 map disc [i don't know if it's only GPS fw on the OEM disc, maybe it contains other soft as well].