I have a MacBook Pro running MacOS Mojave 10.14.6. I also just got a Canon ImageClass MF642Cdw and installed the Scanner Driver and MF Scan v2.15.0. I followed the video and instructions on installing the MF642Cdw on my network via WiFi.
The MF Scan Utility allows me to register the MF printer both through Bonjour and IP. However, when I try to scan using the MF Scan Gear or MacOS Preview, I get error messages and the scan never completes. When I initiate the scan, the printer receives the command to scan the document on the document feeder or platen, but the image never gets sent to my laptop.
The errors I get are attached.
MacOS Preview Error Message When Trying to Scan
Scanner Registered
MF Scan Utility Error
I can print just fine on the Macbook. Don't have a Windows machine to test printing and scanning. I also tried allowing the Canon MF Scan Utility to my MacOS firewall, to no avail. The printer is on when I try to scan and not on standby/sleep mode.