HP 510 - Manual (Page 139)

Unknown ink cartridges.
Press ENTER to continue. The ink cartridges are not recognized by the printer as HP-
approved, and there is at least one that is new.
Press the Enter key.
Unknown paper format
Reload paper The format (roll or sheet) of the paper loaded in the printer is
unknown.
Reload the paper following the normal procedure, to solve this
problem. See
Loading roll paper or Loading sheet paper .
Unknown paper type
Select paper type The type of the paper loaded in the printer is unknown to the printer.
Select a known paper type from the printer menu.
Unknown printheads.
Press ENTER to continue. The printheads are not recognized by the printer as HP-approved,
although the printer can still use them.
Press the Enter key.
Front-panel messages
Message Explanation and action