MY smb connection from mac to windows 10 pc stopped working after working reliably for a year. both computers have hard wire conncetion to network router

My smb connection from mac os x El Capitan (version 10.11.4) to windows 10 pc stopped working after working reliably for a year. both computers have hard wire connection to home network router. File sharing is enabled on Mac and PC. Router indicates both Mac and PC are attached to network and both have normal internet connectivity. File sharing from PC to Mac still works using Remote Desktop Connection on PC. I have tried using IP address of PC (smb://ip of pc) as well as pc name (smb://pcname). I also tried using afp protocol and older command (cfis://pcname or ip address). I cannot successfully ping pc from mac network utiliy nor ping mac from win 10 run accessory. Does anyone have any thoughts on my problem? Thank you

ps here is error message when trying to connect: There was a problem connecting to the server “pcname”.The server may not exist or it is unavailable at this time. Check the server name or IP address, check your network connection, and then try again.