Hi, I'm Sudipto. Welcome to JustAnswer. I'm reviewing your question now, and will post back with your reply ASAP
As you getting a gray scale printing, it means the printer is using color cartridges to make the black color, instead of the black ink. Can you check the ink level and let me know, if the black ink level is showing correctly or not ?
Thanks, ***** ***** have not mentioned anything about trying printhead cleaning, I will recommend you to clean the printhead first and check the result, if the problem persists then, try deep cleaning and check the result again. If the problem persists then, you have to manually clean the printhead. I will give you the instructions later.
Printhead cleaning instructions.
Deep cleaning instructions.