Make sure you purchase the right ink cartridges for your specific printer and printer region or have your old ones refilled. Cartridges are not compatible between different brands, and often not within the same brand. HP often designs its inkjet hardware to use country-specific consumables. When you unbox a new HP inkjet printer and set it up, you install a set of ink tanks that ship with the printer. As you turn on the device and get ready to use it, an initialization sequence localizes it to the country associated with the ink cartridges you installed. HP recommends that you use original HP ink cartridges.
XL (Extra Large) cartridges cost more but do provide better value in the long run. They will be able to print at least double the pages of a regular cartridge. Our advice is that if you print often, go with XL. However, ink can dry up. So if you are not a frequent printer, go with the regular cartridges.
You can check the estimated ink levels from the printer software, control-panel, or the embedded Web server. The control-panel lights indicate status and are useful for diagnosing printing problems. The power light is on (NOT blinking), and one or more of the ink cartridge lights are on (NOT blinking): one or more of the ink cartridges are low on ink and will need to be replaced soon. Get new ink cartridges and replace the existing cartridges when they become empty.
The power light blinks, and one or more of the ink cartridge lights are on (NOT blinking): An ink cartridge is out of ink and must be replaced before you can continue printing. Replace the ink cartridge indicated.
For your US, European and UK HP Officejet Pro K550 Printer you need HP 88 Black (or HP 88XL Black)and and 3 color cartridges: HP 88 Cyan, HP 88 Magenta and HP 88 Yellow (or the XL-versions).
There are also Combo Packs (3 cartridges in one pack) available, like the HP 88XL Value Combo Pack Cyan Magenta and Yellow High Yield Original Ink.
Try Amazon's ink selector tool to find compatible ink cartridges for your printer.
Replace the ink cartridges
6. Hold the cartridge by its sides with the nozzle toward the product, and then insert the cartridge into its color-coded slot. Press the cartridge forward into the slot until it snaps into place. Press down firmly on the cartridge to ensure proper contact.
Align the printhead only if necessary.
Whenever you replace a cartridge or printhead, the device automatically aligns the printheads to ensure the best print quality. However, if the appearance of your printed pages indicates that the printheads are misaligned, you can start the alignment process manually. You can align the printhead from the printer control panel, from the HP printer software and from the embedded web server (EWS).
– Control panel: Press and hold the power button, press the Resume button two times, and release the Power button. The printer prints alignment and calibration pages.
– Toolbox (Windows): Click the Printer Services tab, and then click Align Printheads and follow the onscreen instructions. The printer prints the alignment page.
– Embedded Web server: Click the Settings tab, click Printer Services in the left pane, select Align Printheads from the drop-down list in the Print Quality section, and then click Apply.