we had a problem with Avaya IP Office 11.1.2.4 build 18 embedded Auto Attendant
callers couldn't hear the greeting.
when there was silence if you dialed any number under actions they would work.

so our auto attendant is named Afterhours and under incoming routes, in destinations the dropdown would show AA:01 Afterhours
if we write down manually AA:Afterhours and save it then the greeting plays and everything is ok.

I just wanted to share this workaround in case someone has any problems with auto attendant greeting on 11.1.2.4.0 build 18