Deskjet 6540 printer has been printing pages and envelopes fine until today. Now, it eats envelopes without printing addresses. No error messages. No changes to printer or system. Hardwired link to printer. No other problems with printer. Printing envelope address from MS Word.
Printer rollers may be dirty. Get and use a printer cleaning kit on the printer. I looked at the manual for this model. It is useless for this and there is apparently no service manual. Nonetheless, if you have been using the printer for a length of time, it may be "gummy" and now, today, this day, it is dirty enough to cause problems. Open up the printer as much as you can and clean it as much as you can. Any printer cleaning kit can be used - follow the package instructions about what elements can be cleaned and what not to clean... wear gloves and don't peer at it too closely or wear eye protection (best).
Different envelopes? Likely not... try tucking envelope lip inside envelope? (May be a bad idea, I am not sure how the envelope is read; I think the "lip" portion is benign.)