Canon S400 Reference Manual page 201

Seven flashes: BJ Cartridge defective
There is a problem with one of the BJ Cartridges mounted in the printer.
Remove each BJ Cartridge and check that the contacts on the BJ Cartridge
and cartridge holder are clean. Also check that the orange protective tape
has been removed from the print head then install the BJ Cartridge again.
If the error occurs again after you resume operation, replace the BJ Car-
tridge.
Eight flashes: Waste ink tank almost full
The printer has a built-in waste ink tank to hold the ink that was consumed
during print head cleaning. Eight flashes indicate the waste ink tank is
nearly full. Press the RESUME button to skip the error so you can continue
printing. To prevent the ink waste tank from becoming full, call for help to
have the waste ink tank replaced immediately.
When the waste ink tank becomes full, the POWER lamp flashes orange
Note
and green alternately, and printing will no longer be possible.
Call for help to have the waste ink tank replaced immediately.
Replacing the BJ Cartridge
Troubleshooting - The POWER Lamp Flashes Orange 201