DIAGNOSIS The print head nozzles for the black ink are clogged with dried ink. This is super common with these inkjet printers if they sit unused for a week or two, especially with the standard dye-based black ink.
FIX You need to run a deep cleaning cycle from your computer. 1) On your PC or Mac, go to your printer settings (Devices and Printers on Windows). 2) Right-click on your TS3520, select ‘Printing Preferences’, then go to the ‘Maintenance’ tab. 3) Click ‘Deep Cleaning’. Select the black ink channel and run it. This uses a fair bit of ink to force fresh ink through the clogs. After it finishes, print a nozzle check pattern (also in the Maintenance tab) to see if the lines are solid.
IF THAT DIDN'T WORK If the deep cleaning doesn’t clear it, you can try a manual clean. Dampen a paper towel with distilled water, place it in the tray under the print head parking station (where the head sits when off), and gently park the print head on it for about 10 minutes. The moisture can help soften the dried ink. Then run another deep cleaning cycle.
HEADS UP Don’t run the deep cleaning cycle more than twice in a row—it will drain your ink cartridge fast. If it’s still clogged after two tries, the cartridge itself might be faulty even if it reports full, or the print head may need replacement.