Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
The first best thing to try for this error message is, on the printer, press
and set the paper setup size to match the envelope or other stock that is loaded in the printer (and match the size in the settings too. Note: if you get width and length mixed up, the printer will reject the setting as wrong.)
If that doesn't help, let me know the dimension of the envelope stock used, and whether you have a Windows or an Apple computer that you are printing from, and I will advise you further. Thanks.
If the above solves the problem, great! and please rate my answer so that this case may be closed.