Yeah they are only accepted in store now. ToysRUsTradeInCenter.com stopped working around 5 or 6 weeks ago since Gamer's Factory who handled the trade ins for TRU are is no longer working with TRU and might be shutting down themselves since GamersFactory.com also stopped working at the same time (but they are still selling on EBay, but that might be to get rid of the stock they currently have).
Values on older games can be good, but for newer games not so much.