DIAGNOSIS The printer is on the network, but your computer isn't discovering it. This is almost always a firewall or network profile issue on the computer, treating your home network as 'Public'.
FIX First, verify the printer's IP address. On the printer control panel, press Home -> Setup -> Network Settings -> View Network Status. Note the IP address. On your Windows PC, open 'Devices and Printers', click 'Add a printer', and choose 'The printer that I want isn't listed'. Select 'Add a printer using a TCP/IP address' and enter the IP address you noted. This bypasses discovery.
IF THAT DIDN'T WORK On your computer, check the network profile. In Windows Network Settings, ensure your Wi-Fi network is set to 'Private', not 'Public'. A Public network blocks device discovery. Also, temporarily disable any third-party antivirus or firewall software to see if it's the blocker.
HEADS UP The ET-2800 doesn't support Apple AirPrint or Google Cloud Print as robustly as some. For Apple devices, make sure both the printer and your iPhone/iPad are on the exact same 2.4GHz Wi-Fi network (not one on 5GHz). Sometimes the Epson Smart Panel app is more reliable for iOS printing than the built-in AirPrint.