Are you using branded Epson paper? Spurious brands can sometimes perform poorly in certain printers.
My HP won't feed any type of photo paper other than branded HP paper. I'm sure HP didn't build this feature into the printer.... ahem.
Alternatively, are you sure that this model of printer is designed to use 6 x 4 paper? The fact that the roller stops turning suggests the possibility that the printer isn't sensing the paper.
Maybe try printing in landscape format and turning the paper around so that feeds in the long edge. I've no idea whether that will work, but it's worth a try. Check your manual first, though, to make sure that's OK.