Envy 7640 all-in-one prntr jam msg I cannot clear, have done all suggestions to clear, still jammed

I have an Envy 7640 All-in-One printer that keeps telling me there is a paper jam, but there is no visible paper jam anywhere.  This has happened 4 or 5 times since last summer.  I have reinstalled software more than once and followed all the suggestions to try and clear it.  I cannot find a "rear access door" on it.  Is there actually one, and how do I open it to look?  Nothing back there looks like a door and nothing opens.  I'm sick of this and ready to go buy a new printer that ISN'T AN HP PRODUCT!!