There is an active disucssion going on in the Apple community forum that you may want to follow as well. I am still investigation this sisue to see if it's an issue with Canon's Bonjour implementaiton, an issue with OS X or an issue with my WiFi system. Again, a 'fix' is to use a hard-coded IP address and the LPD protocol, but that's less than ideal because it means I need to configure my router to always handout the same IP address to the printers (or to not assign IP adresse in the range I configure the printers to use a static IP in). Nothing has changed on my side, other than the 'upgrade' to macOS Sierra beta. These printers will periodically go offline with both Macs. Has anyone noticed slow speeds while on WiFi on macOS Sierra My Link speed is fine, 1300Mbps, yet I can no longer achieve my normal 150+Mbps downstream via WiFi. I am having other issues with Canon printers (MF733C and 6230) connected via WiFi and using Bonjour. For my small office environment that was an adequate solution but it was way more work than I had hoped for. Basically, when you connect a Sierra mac to the corporate WPA Enterprsie WiFi, Sierra will always request for you to validate the certificate, even after marking the cert as 'Always Trusted.' On first connection it gives an error: 'This certificate is not valid (empty subject name)' Its an X509 cert. I 'solved' the issue by hard-wiring the printer to my Ethernet switch and using the Canon IJ Network protocol. I have this printer and have both Sierra and High Sierra and have experienced the 'printer offline' issue when the printer is conncted via WiFi and using Bonjour.
