I have Scanlite, Xsane and Simple Scan. A ll downloaded and in the launcher. They all recognise there is a Canon MX420 printer but non of them scan, one of them says there is an I/O problem. Libre Office recognises the printer and prints OK. I'm just guessing its the scanner driver, I've searched for one but no luck so far. I also have an HP printer (recently had problems) which may be better compatible. If the problem persists I might try that.
Going to unload Scanite, though its is spelt on my computer as Scanlite, but that doesn't matter now.