Not compatible with HP Envy 4520
Neither of the two cartridges purchased are recognised by my HP Envy 4520 printer. Despite their correct installation (!) only the original HP colour cartridge is recognised and this is the one that will be used to print even the black and white pages. Re-installing an original HP black ink cartridge and everything is back to normal.
Having tested both cartridges I have no hope of a refund.