ro32,
Welcome to the HP Forum.
If you have never done so, this might be a good opportunity to clean the printer. The error message may be symptomatic of a bit of dirt.
Consider the steps recommended for cleaning the printer in this document:
A 'Paper Jam' Message Displays on the Control Panel
In particular, note Solution Four.
I do realize that you are not reporting a paper jam.
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You might also check the following:
Error messages displayed on computer> Windows 7 >
'Paper Mismatch,' or 'Paper Size Mismatch' Error Message Displays When Printing in Microsoft Word
There are other docs and such that may be helpful at your printer's website, be sure to take a look around at what is available.
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Although I strive to reflect HP's best practices, I do not work for HP.