Canon Pixma MG3550 Online Manual page 646

If the problem is not resolved after cleaning the print head twice:
Step 3
Clean the print head deeply.
From the machine
Cleaning the Print Head Deeply
From the computer
Cleaning the Print Heads from Your Computer
If the problem is not resolved, turn off the power and clean the print
head deeply again after 24 hours.
If the problem is still not resolved:
Step 4
Replace a FINE cartridge.
Replacing a FINE Cartridge
Note
If the problem is still not resolved after replacing the FINE cartridge, contact the service center.
When the Print Results Are Not Even such as the Ruled Lines Are Misaligned:
Align the print head.
From the machine
Aligning the Print Head
From the computer
Aligning the Print Head Position Automatically from Your Computer
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