Canon TR8620 printer not printing in macOS Sequoia 15.2

Are these the drivers you downloaded?

Did you remove the printer and try to add it back with the Apple menu -> System Settings -> Printers?

If not present, did you try to add the printer with the Option key held down?

Option key forces the installation of any drivers developed as open source drivers which many printers actually use.

If the printer is on WiFi, is it on the same network as your Mac?

Did you attempt to reconnect the printer to the same WiFi after removing it?

Do you have a USB printer cable to connect the Mac to the printer, and try running the add printer option through the settings with USB?

The Canon TR8620 is listed as supported in About AirPrint - Apple Support (en-us edition, January 13, 2025), so if the printer is connected to the same network (Wi-Fi router) as the macOS Sequoia 15 Mac, additional drivers should not be needed for printing.

AirPrint works with wireless (Wi-Fi) or wired (Ethernet) network connections. This means that you could connect the printer by Ethernet cable to one of the LAN ports of the Wi-Fi router instead. This may be more stable, and some of the difficulties related to wireless connections can be avoided.

Make sure that your printer has the latest firmware. If necessary, update.