Why is printer not printing all lines but skips every 2-3 lines wf3640

It’s caused by air in the printhead or a persistent clog in the Epson printers 100% of the time. If you used OEM ink, their OEM formulation is thick to the point of easily taking down the printer without manual cleaning. 3rd party ink isn’t as thick (generally) but you are still dealing with a printer that clogs for no good reason other then it apparently wants to. Find a good set of compatibles or refillables, good pigment base ink (dye will require a total system flush) and ditch the OEM Epson ink in this one! DON’T UPDATE THE FIRMWARE EITHER.

What you need to do is try purging the air from the head, since this is one of those either or failures so start there - refer to this video to fix it if it’s air (and positively know). if it’s clogged, you can find a cleaning kit on eBay that’s designed to deal with Epson printers. If it’s really bad, the printer needs to be taken apart and the head needs to go into a untrasonic cleaner. If you see an error like this you’re in trouble if you can’t take it apart.

The WF-3640 is particularly sensitive to clogging since it uses one of the early PrecisionCore heads without backup nozzles (or a meaningful amount) and has a weak printhead system that LOVES to error out when it’s fatally clogged.