Workforce Pro 7840:
Tried all this and it didn't work (updated recovery I think) but I did buy these [link|https://www.amazon.com/dp/B0D127FXCM?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1&tag=ifixitam-20|https://www.amazon.com/dp/B0D127FXCM?ref...|new_window=true]
(812XL Ink Cartridges High Yield Remanufactured Replacement for Epson 812 XL T812XL 812 to use with WF-7820 WF-7840 WF-7310 EC-C7000 P) for 42.99 swapped the chips out and worked perfectly AND I don't need to change them as they are not one use!