Canon 640 will not load & print from rear tray after installing Serria?
Please Note: There are currently no macOS 10.12 Sierra printer drivers available for PIXMA products. This issue is being investigated and we hope to have these drivers available soon.
I guess you'll either have to wait, or go back to El Capitan.
It's always wise to check compatibility for mission-critical apps & devices before jumping to a new OS.