Diagnosis
Wireless setup on this model can be finicky, especially with modern routers using combined 2.4/5GHz bands or certain security settings.
How to Fix It
First, try the WPS method if your router has a WPS button. On the printer, go to Menu > Network > WLAN > WPS Setup. Press the WPS button on your router within 2 minutes. If that's not an option, use the 'Standard' setup but ensure your phone/computer is connected to the 2.4GHz band (the printer doesn't support 5GHz). Manually type the network password, watching for case sensitivity.
If That Didn't Work
Temporarily disable any advanced router security like 'AP Isolation' or 'Client Isolation'. Also, if your network name (SSID) has special characters or spaces, try simplifying it for the setup process.
Heads Up
The printer's wireless setup really doesn't like hidden SSIDs. Make your network visible temporarily during setup. Also, its wireless card isn't the strongest, so keep it within a reasonable range of the router.