Answer key ignores call

[Gulanowski]

I thought that it had been that the person calling hung up just as I hit the answer key (green telephone symbol of course) but it's been happening frequently enough so that I've come to the conclusion that when I hit the answer key for an incoming call the call is ignored/ended instead of answering it, the phone menu doesn't even come up. Has anyone else experienced this, and if so how can I fix it?