HP DeskJet GT 5820 - Manual (Page 95)

e. Check if there is a plug on top of the printhead or plastic tape on the printhead contacts. If there is,
remove the plug from top of the printhead and the plastic tape from contacts.
NOTE: Do not touch the electrical contacts on the printhead.
f. Slide the printhead into the slot until it clicks into place.
g. Firmly close the blue printhead latch.
h. Close the printhead access door.
ENWW Printhead issues 89