Just speculating, but there are many reasons why the listing agent may not have responded, assuming she received offer:
-->The owners received your offer and didn't like it. You believe your offer was fair. Perhaps it was. Nevertheless, maybe the owners didn't think it was fair. Or that it was fair, but that it was lower than they could accept.
-->The owners received your offer but weren't in a position to make a decision that quickly. Not that 72 hours is unreasonable; that generally is a good thing to do. But sometimes people just don't or act quickly.
What to do now? First, ask your agent for any insight he/she can provide. If you really want the house, make another offer. It can be the same as you made before, or higher, or lower. Your choice. But now you see why it's important to figure out, with your agent's help, why there wasn't a response.
Understand that the sellers aren't required to respond to your offer. Perhaps it would be polite to do so. And it would have made sense, from the sellers' standpoint, if they felt your offer was worth pursuing. But they weren't obligated to do so.
Hope that helps.
You don't mention whether you're working with the listing agent directly, or with another agent, but, certainly, you have every right to expect a response from the listing side.
The agent may be having difficulty reaching the Seller, but still, you should be told this. Even if the Seller has no interest in your offer, you need to know what's going on.
Occasionally, I have encountered the situation where a listing broker who runs a one-agent office goes on vacation and doesn't leave anyone to cover his/her business. Unless your agent IS that agent, your agent should be keeping you up-to-date. What does your agent say?
If you write another offer (or present the same one again), have your agent ask to be there when the offer is presented. Good luck.
Maggie Hawk, REALTOR
Watson Realty Corp.