Diagnosis
The LBP236dw's wireless setup is notoriously finicky with certain router settings, especially if you're using a 5GHz network or WPA3 security.
How to Fix It
The most reliable method is to connect it via USB cable to a computer first. Use the Canon software from the website to set up the wireless settings through the 'Remote UI' (the printer's web interface). Once you input your 2.4GHz network name and password there, you can disconnect the USB. Alternatively, use the WPS button method if your router has one: press and hold the wifi button on the printer's control panel until the light flashes, then press your router's WPS button within 2 minutes.
If That Didn't Work
If it consistently can't see any networks, there might be an issue with the printer's wireless module. Perform a full reset on the network settings: Go to Device Settings > Reset Settings > Reset LAN Settings.
Heads Up
This printer only supports 2.4GHz WiFi bands. If your router broadcasts a combined SSID for 2.4 and 5GHz, you might need to temporarily split them into two separate network names in your router settings to get the printer to connect reliably.