Would you believe it! The black cartridge is now working fine.
I previously took out the black cart due to the error message. Evidently due to overfilling with bulk ink the contacts were dirty due to leaking ink.
I cleaned the dirty contacts on the side of the cart and also the contacts on the inside of the printer with a Q tip and alcohol and reinserted it but the error message still indicated a faulty cart.
Then I removed the black cart and put it in a plastic bag and returned the printer to my friend and told him to change the black cart to resolve the issue.
After a few days my friend told me he reinserted the black cart and its working fine.
I suspect that removing the black cartridge and leaving the printer off a few days helped the circuit board to dry out from contaminated ink. Another possibility is that leaving the printer with no power for a period of time somehow helped to stabilise it and clear the error. Useful to know in case of a future problem.
Kind Regards
Chris