DIAGNOSIS This is almost always a router communication issue, specifically with the 2.4 GHz band. The TS3520 does not connect to 5 GHz networks, and certain router settings (like WPA3-only mode or certain channel widths) can block it.
FIX 1) On your router’s admin page, ensure your 2.4 GHz network is turned on and broadcasting its SSID (network name). 2) Temporarily set the security to WPA2-Personal (AES). 3) Make sure you’re entering the password correctly—it’s case-sensitive. 4) During printer setup, choose the “Standard setup” method, not WPS. 5) Move the printer and router closer together, away from microwaves or cordless phone bases, just for the setup.
IF THAT DIDN'T WORK Try connecting using the Wireless Direct method first. Press the Wi-Fi button on the printer until the light flashes, then connect your phone/computer directly to the printer’s network (name will be on the printed info sheet) to run the setup wizard from the Canon app. This often bypasses the initial router hang-up.
HEADS UP If your router combines 2.4 and 5 GHz under one name (band steering), the printer will often fail. The most reliable fix is to temporarily create a separate 2.4 GHz network with a different name for the printer setup.