To dream of an answering machine represents ideas, insights, advice, or clear instructions that were given to you when you weren't listening to it. "Nobody was home" when something important was said. Feeling that you didn't listen to someone enough when it was important.
Negatively, to dream of an answering machine represents ideas, insights, or advice that you aren't listening to. You've "gotten the message", but aren't doing anything about it. You may have difficulties or frustration in understanding an idea or viewpoint. Something isn't "hitting home" as quickly as it should be. Willfully ignoring advice in the present because you have more important things to do. Preferring to enjoy yourself not having to be concerned a problem until it becomes a big problem.
Example: A man dreamed of his father leaving a message on his answering machine. In real life he was experiencing a moral dilemma with consequences that he was well aware of. His father on the answering machine represented the decision to do the right thing (conscience) being willfully ignored until he was ready to listen to it.
Example 2: A man dreamed of hearing a badly garbled message on an answering machine from his father. In waking life his father had died and he couldn't remember what his father had told him to do about certain property issues after is death.