My G4210 has the same problem quite frequently. I don't recommend using the ink flush or cleaning routines. Instead, create a document with some Purple colored rectangles side-by-side and print those. This will quickly get the Magenta ink coming out ...
There was another incident like this one where an error message appeared in the display and the printer wouldn't print anymore. The error message said to contact my Cannon Service Center. I called Canon and the representative told me that I for the E...