I suggest that you take a look at Final Burn Alpha and gngeo sources. Sound support is a bit tricky to get working. Also make sure that your memory and Z80 port handlers are set-up correctly.
PS: I am a Neogeo emu author :) (download the beta version from http://www.mytempdir.com/2022594)
> Any NeoGeo authors have any tips about getting sound to work?
> I have the Z80 running, and I pass the bios Z80 check. However, the ym2610
> never gets a request to start an adpcm channel (I don't even care about the FM
> stuff yet).
> I have the ym2610 timers running, and I've verified they are sending IRQs to the
> Z80. I'm giving the Z80 a NMI when the 68k sends a sound command.
> I don't have much debugging capability on my target system, so it's hard for me
> to track down problems. Any insights would be very much appreciated.