When I try to copy or scan from the glass it tries to feed from the automatic feeder tray instead.

Click the "Edit" tab, make sure the "SADF" is not enable...

Try using the HP Scan Diagnostic Utility in Windows - HP Customer Care (United States - English).

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This black line sounds like it is definately coming from the ADF scanner glass. This is the thinner strip of glass that is located just to the left of the large original glass. You can verify this by making a copy from the large glass instead of using the feeder on top. If the copy comes out clean then it is definately the scanner glass. Just clean the glass well with glass cleaner and a soft cloth. This glass is only used when copying/scanning using the top automatic feeder
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The most common cause of blank (void) lines on a scanned document is from whiteout on the glass where the page is scanned when using the document feeder.
If there is a clear mylar sheet on the bottom of the document feeder, the whiteout may be there instead.

If there was dirt or a dark smudge on the glass (or mylar), it would show up as a black line, but whiteout is white, and shows up as a void (blank) line.

You have a piece of dirt or whiteout on the scanner glass. When the paper is moving by, it creates a "Line" if the paper is sitting still on the glass, it may be a dot or it may even use a different glass alltogether for ADF vs Paltten scanning.

look to the side of your big glass and you'll see a piece of glass about 1.5" wide. thats the galss that is used for scanning from the feeder. theres got to be something on that glass. possibly white-out or even a small speck of toner can cause that. look closely.

hth,
razors

If the lines are vertical (in the direction the ADF feeds, 11in long for 8 1/2 by 11) You can try cleaning the glass the scanner uses when it's using the document feeder. Pull up the top left part of the printer where the documents feed, there's a little rib in the middle of the side to help you do this, then simply pull up the assembly underneath with all the rollers in it, you should see about an inch of glass underneath and a centimeter long strip of white plastic on the assembly (this serves as the white background when feeding slimmer papers) Clean them both. I'd recomend any glass cleaner, just don't spray it in there, spray it onto a cloth.

chances are the feeder isnt feeding the paper at all, thats why you cant scan a single paper, try opening up the ADF and clean the feed rollers first, turn off the machine and gently rub the rollers again and again until you have a clean shot or surface, try this from thop to bottom rollers, please make sure though to insert uncreased paper and paper without eardogs on its leading edge, this could cause some delay upon feeding process

sometimes because it is exposed to dust, there is a tendency for the rolllers to slip, or you could be having a broken part that drives the feed rollers from your ADF.

Regular copy paper that I got from the Staples. Same paper in the paper tray/drawer as in the multi-bypass tray. Thanks.

If the paper isn't feeding in the ADF (automatic document feeder - upper paper feeder) then the ADF roller assembly will need to be replaced. Try a copy on the flat glass area. If it work, then it's the ADF, If not then the upper scanner assembly with have to be replaced.