Canon S400 Reference Manual page 179

Print job does not start
Check 4
Are you using the correct printer driver?
A print job may not start if you have selected the wrong printer driver for the
print job.
Make sure "Canon S400" is displayed in the Name entry box of the Print
Windows
dialogue box. If another driver is selected, click the down-arrow and select
"Canon S400" from the pull-down list. If S400 does not appear in the list,
you must install the printer driver.
Note If you use only the S400, select the S400 as the default printer.
Select S400 from Chooser of the Apple menu.
Macintosh
Troubleshooting - Printer Does Not Start or Stops in Mid-job 179