Hey there!
Usually re-installing the software will resolve this problem. Head to https://canon.us/MG3620setup and follow the prompts. It will walk you through the uninstall/reinstall process.
Please keep in mind that this printer is only compatible with the 2.4GHz spectrum, so you want to make sure your new router is broadcasting the older 2.4GHz alongside the newer 5GHz. Your router can't broadcast "WiFi 6 only," or the printer can't see it. Don't worry about your WiFi unless you have a problem with the printer not being seen during the re-install.
Let me know how it goes! 😊
