If the pattern of missing line position does not change after each cleaning, always in a fixed position, it indicates that the print head blocked. If the position of the missing line is variable, it is not a plug but a disconnection. It is normal when changing the ink box (or after adding ink)there is a disconnection. In general it will be ok after cleaning once or twice, and each time the disconnection will be less after cleaning (Attention: it is better to do the second cleaning 20 minutes or more later after the first cleaning.). When there is a disconnection in use, and it is more after each cleaning, this is because there is no ink in the ink box, and the ink box should be replaced immediately.