You cant activate any audio inputs when Max is a slave (using ad_rewire driver) - the audio is driven by the host application.
What you can do in this case is to send audio and midi to the host, and receive midi and infos (hostsync~) from the host.
If you want to have an external instrument trigger things you should deal with midi, or use Max as an host (using rewire~ and something like Reason)
hope this helps
Have a look at this patch. Double click on midi in and the menu - to select the relevant setting that you have chosen for appleton to send through data and the umenu. This should do what you are after - not sure how to connect it but hope this helps.