You can try to disassemble the printhead and check for contamination.
First remove cap 1
than using a small flat screwdriver disassemble printhead (engagement points 2 and 3)
Warning - a printhead is filled with 8 ml ink
After disassembly - clean the printhead with fluid compatible with pigment ink (for black color) or compatible with water based ink (color printheads)
during reassembly - don't forget to fill the printhead with ink (2/3 of its volume)