Check if MAC address filtering is disabled. If it is enabled, register the printer’s MAC address so that it is not filtered. See the documentation provided with the wireless router for details. You can check the printer’s MAC address from the Network Status part on the network connection report.
If your wireless router is using shared authentication with WEP security, make sure the authentication key and index are correct.
If the number of connectable devices on the wireless router is less than the number of network devices that you want to connect, make settings on the wireless router to increase the number of connectable devices. See the documentation provided with the wireless router to make settings.