The out of ink error is because your chips are registering as too low to do the charge. The chips and actual ink level in the cartridges are not kept in sync by a sensor only by approximation as you print ink out of the printer’s head (or during a clean).
So, you need to identify which chips are registering as low and get replacement chips for them.
These cartridges are small (they match Epson in mL) and this has been a recurring problem with users not filling the carts enough. We have come out with a totally unique design at InkjetMall (solely for our customers!) that fixes this issue. https://shop.inkjetmall.com/ReUsable-Cart-Kit-with-Syringes-R3000-v2-Set-9.html Now we sell 60mL carts for both the R3000 and P600.