A good recommendation is for your agent to contact the listing agent regarding the delay in getting a response for your offer. Some banks require a waiting time before they will respond to offers. There may be a problem with the property that is causing the bank to wait in responding to your offer. Maybe there is another offer that fell out of escrow that the bank is waiting for cancellation before accepting another offer. You need to do some investigation to find what is occurring.
That's a long time. I'm assuming you used a real estate agent, so ask your agent to get you an answer. There are really only 3 answers the bank can give: acceptance of the offer, rejection of the offer, or a counteroffer. Typically on a foreclosure, one of these three answers will be provided in 24-72 hours. Anything more than that and it needs follow-up to ensure the offer was received and considered.