Epson Artisan 835 black ink not printing

I purchased the ACC-110 Flush Kit hoping it would clean the black channel in an Epson Artisan 835. I have been using your InkThrift CL with no problem until the black recently stopped printing anything. I put 40ml or more of the cleaning solution into the cartridge opening but still nothing came out the print head. I tried 2 cleanings but the black continues to print nothing. Has the black print head failed as all the other colors are perfect? I looked at the cleaning video so I don’t know what to try next.
Thanks for any suggestion. Bruce