No. Sellers are never required to accept an offer, even if it's full price. As someone else asked, do you have an contingencies in your offer? Such as that it needs to appraise at the sale price, or that you need to obtain a mortgage for a certain amount, or did you ask for closing costs, did you ask for all satisfactory inspections, etc.? Even if you offered full price, someone else may come along and offer less money but not have any (or less) contingencies in their offer which some sellers think is a "better" offer because they have less things to worry about / deal with. So full price doesn't always guarantee that you will get the house.
Has your agent been in touch with the sellers agent? Your agent may be able to get you some additional information, such as if there is another offer on the table. If there is, you can go back with your best & final offer (which may include taking out contingencies, if you have any in the current offer).
Good luck and I hope you get the house you want!