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I have a brand new PIXMA Pro 200. I'm trying to print on a 5x7 card and it worked the first time I did it. Now I'm trying to do it again and I'm getting an error message that says "the size or type of paper loaded into the top tray is different from ...

I'm trying to print on an A7 envelope (5.25x7.25) and the printer keeps feeding the envelope through and spitting it out without printing anything. Does anyone know what I could be doing wrong?