This is most often because of a bad or jammed sensor. The printer begins feeding the paper and if the paper doesn't trip a sensor that tells the printer the paper has arrived, then the printer thinks the paper has jammed on the way there.
Depending on the printer and the sensor this can mean different things. Some sensors are light-sensing "electric eye" types that look for the paper to go between an emitter and detector, often in one little housing that looks like a little square C. If this is blocked or if ink is staining either side, then it may not detect paper properly. On other printers there is a little plastic lever and if that gets blocked or jammed with little paper bits then it has the same effect. The real problem is on those printers that have a photo-scanner type sensor. Some printers have a little miniature photographic scanner, similar to a document scanner, co-mounted with the print head. It uses that mini scanner for several purposes, it can use it for automated "alignment", it prints lines then scans them to see if they are straight. It also uses it to detect when the paper is in the right position. Unfortunately it is susceptible to getting ink stains on it because, as I said, it's right by the print head.
What is the model of printer? What has Epson said?