Samsung SL-M4020ND-TAA - Manual (Page 166)

Wireless network setup
166 2. Using a Network-Connected Machine
Connecting Failure - SSID Not Found
• The machine is unable to find the network name (SSID) you have selected or
entered. Check the network name (SSID) on your access point and try
connecting again.
• Your access point is not turned on. Turn on your access point.