Can't see network shares

Hi, I currently have two PC's - a Windows 7 desktop which is ethernet attached (PC-A) and a Windows 8.1 laptop (PC-B) which is wireless. Until the other day, the two PC's were able to see each other and access each other in Network Places and both could see the router and the network printer attached to PC-A. Now, however, PC-A sees only the router. It does not see itself or PC-B and the...