When you dial the announcement extension by hand, do you hear it then? Also, like Brandaris mentioned, you have to test this by calling from an outside line to the VDN, not internal, and it will only be heard by the agent, not the caller.
You say you modified the COR for the VDN, but did you modify it also for the agent or station? Be aware that with EAS the logical agent COR is leading, not the station COR..
There are a lot of interactions with other features, like VDN override etc, consult your manual for details (or in plain English: RTFM!

), if you don't have it, take a look at
, the site will take a while to get used to, but there's a lot of info on it.
Cheers,
Nico