What can I do when my Macbookpro fails to "find" and connect with Canon printer TR8520

This device is supported by Apple's built-in AirPrint drivers which supersede the need for Canon drivers. If it is configured wireless/wired, it will be discovered by Apple's Bonjour service, but only if on the same subnet (ideally with a static DHCP address outside of your normal DHCP range) and without any USB cables connected.

re: "finding"

Apple uses Bonjour/Discovery protocol to quickly and easily locate devices and services on your local network. but it requires a special setting in your network interface:

IPv6:

System Preferences > Network > Wi-Fi|Ethernet > (advanced) >TCP/IP > IPv6

... to Link-local only

ON may cause routing activity that interferes with your networking.

OFF will make it hard to find printers and other services on your network.

An easy first step is to power-cycle your wireless router. While you do that, you might as well do the same with the printer.

Unplug their power cords, wait a moment, plug them back in again.