Why Does My HP Envy 7155 Printer Keeps Saying Out of Paper?

Every time my HP Envy photo 7155 all-in-one series printer keeps saying out of paper error. The input tray has already been filled with 20 sheets. I don’t know what is wrong. I have unplugged it twice, turned it off, and even taken the paper out, still facing the same error. Please help.
Response by [Kelvin Morton]
Thank you, Mister, for writing us the printer issue. The out-of-paper error mostly occurs because of incorrect paper settings, outdated firmware, or mechanical issues with input and output trays.

This paper-related error is fixable easily with the help of our detailed blog to resolve HP printer says out of paper error but has paper.