I have the same problem with my photo paper cassette tray. I also have the Epson 837 printer. I have been able to get my photos printed by using a work around solution. There is a small tab on both sides of the photo tray and it looks like one of the tabs has broken off. Probably when I pulled the tray out of the printer. The photo tray doesn’t stay all the way to the front of the paper tray and that’s the problem. I used a small wooden dowel and pushed the photo tray all the way to the front while pushing the paper tray all the way in. This is now printing photos every time. Give it a try. What can it hurt?