All inks are full and working fine except black.

This is a common problem with Epson printers to the point it’s not hard to diagnose if you know what to look for. Since your printer uses DuraBrite Ultra ink, the clog rate is even worse then the dye based models. The issue with Epson pigment ink is the ink is thicker then ANY OTHER pigment base ink, which makes the printers more prone to clogging. This is a well known issue with Epson pigment base ink.

Anyway, since this is just a common “consumer oritented” model, don’t bother taking it to a shop for unclogging. For yours, buy the Epson printhead cleaning fluid kit and unclog it yourself, which is easily found on eBay. If this doesn't work it's an air or printhead issue you cannot fix without a new printhead.

If it's an air problem, inject compatible ink into the printhead directly and “force” the air out. DO NOT USE GENERIC PIGMENT INK; THIS CAN DAMAGE THE PRINTER IF THEY BIND. Your best bet for the ink is to buy a bunch of genuine ink for from someone who purchased a small stock (or get a few 200-I ink lots), only to have an issue with the printer. However, “100% compatible” bulk ink from a company that specializes with Epson printers can also be used but if it is not entirely compatible the risk of a ink binding issue destroying the printhead comes into play again.

After you fix it, remember to run it at least 1-2 times a week. This is a must to keep the ink in the system from drying up with how bad many of these pigment machines clog from non-use. Anything will do, but a nozzle check will probably be the best way to be sure it isn’t a problem again, if you have the Epson Toolbox installed.