Why does the Realtor always get the blame? When things go wrong, most times its caused by the actions (or in-actions possibly in this case) of the buyer or seller of a property, not their agents. We do our best to present all offers as soon as possible, but we can't make a seller respond by the deadlines contained in the offer (which does not become a contract until signed by all parties, and the deposit is received). Without knowing all the circumstances in this case (as other have said), it's impossible to know what is going on. I'm assuming you are using a buyer's agent, who should be following up with the listing agent and communicating back to you with what is going on. If you are not using a buyer's agent, and went directly to the listing agent, well then, good luck. You have no one representing you (unless you are using an attorney).
If your offer was in the ballpark of being a reasonable offer, then you should hear back from the seller. Delays like this happen quite often in this business, especially if there are multiple sellers involved. It could also be that the listing agent was expecting another offer, and the seller is delaying the response to yours until he/she sees what else comes in. The listing agent is trying to get the best price for his seller, but he also doesn't want to lose a good offer that is on the table (yours) just to see if a better offer comes in.