My DVD / CD tray is being rejected when I start to print directly onto the DVD. It takes several attempts at re-inserting the tray before the printer will start printing.

The tray is for the DVD or CD itself, not for a label. The printer prints directly on the CD or DVD, you must use ink jet compatible blank disks, the white ones with no printing. You don't need a tray to print the label.

Did you follow the steps from the user manual for this printer to print to a CD/DVD label? do you have the user manual for this printer if not you can downlaod it from here http://h10032.www1.hp.com/ctg/Manual/c01507549.pdf

Please follow these steps:
1.
Turn your printer on. Most power buttons are located on the top of the printer. Press and hold down the button until its LED light turns green.
2.
Choose the image or text you desire to print onto the CD. On your computer, open the image or text you desire to print. images should be opened by clicking on your computer's "Start" icon and selecting the "Pictures" tab folder within the Start menu. When the Pictures folder opens, click on the image you desire to print onto the CD to enlarge it. If you are planning to print text onto the CD, open the text in Microsoft Word or any other desktop publishing program you may have on your computer.
3.
Insert the CD into the printer. Press the "Eject" button that can be found on your CD printing enabled printer. A CD tray will open automatically. Place the CD into the tray print side up. Close the CD tray. The printer will begin working to detect the CD. Once the CD is detected, your printer's LED light will either flash green or another indication color.
4.
Print the image or text onto the CD. For image printing, click on the enlarged image's tab that will be on your computer's taskbar. You will see a horizontal row of action icons below the image. Click on the thumbnail image of a printer to print the image onto the disc. For text printing, simply click on the "File" action on the navigation menu in your desktop publishing document. Click "Print" within the "File" drop down menu. The image or text will be sent to the printer once you choose the "Print" action.
5 .
Remove the CD from the printing tray. The CD will be fed through the printer during the printing process. Once the process is complete, the CD will come through the bottom of the printing tray. Take the CD from the tray when it reaches the bottom.
The above mentioned steps must help you. In case of any difficulty please revert back.

1. Find a printer that prints directly on a CD; this is becoming a popular feature and these printers are getting more affordable.
   
2. Step 2 Buy some printable media. Printable media is a bit harder to find and a bit more expensive but you need a special surface that will absorb the ink. They will be marketed as "inkjet printable" discs. Look for them online or at your electronics store.
   
3. Step 3 Set up your printer for CD-R printing. Chances are your printer can print on paper and CDs, so you'll have to let your printer know what you are up to. In your printer properties, select CD or DVD as your media type. You can do this from the print dialog right before you print.
   
4. Step 4 Clean the rollers. You can do this by running a clean sheet of paper through the printer without printing anything. Load up several sheets of paper and press the cancel button to feed it through. Do this a couple times.
   
5. Step 5 Pull out the tray. This may be a separate part of your printer or built-in. Read the manual and learn how to pull it out properly before you go yanking at random and breaking things.
   
6. Step 6 Place the CD in the tray. Make sure there is no dust or paper scraps on the tray and place the CD on the tray so it lies flat and the printable side is facing up. For smaller CDs, place the adapter first and then put the CD down.
   
7. Step 7 Insert the CD tray into the printer. If the tray was attached to the printer, put it back where it came from. For separate trays you may need to wait until you are ready to print and load it into the manual feed.
   
8. Step 8 Design your label. Your printer will have come with label designing software. Take some time. Make it pretty.
   
9. Step 9 Print. Double check your print settings and print directly onto your CD. Choose "File" then "Print" and click "Okay." If you are loading manually, now is the time. Manual loading slots are usually on the back.
   
10. Step 10 Allow your CD to dry. It is recommended to let it sit for 24 hours. There is a lot of ink on there and you do not want to ruin it with smudges.
    

>> It tells me to close the door so it can resume printing on paper normally A4.

It is trying to "ignore" the "bypass" try.

Tell the printer to *ACCEPT* the disk from the "bypass" tray,
rather than from the stack of paper in the A4 tray.

To tell the printer, click the OK button on the printer.

Have you select the media in printer setup?

I am trying to print on DVD with Canon MP810 but the image won't line up - seems to be taking the tray too far in and printing some of the image on the F tray! Help.... it's driving me nuts

This solution is taken from the HP website.

Follow these steps to print on a CD or DVD.

1. Make sure that the CD/DVD tray is completely closed (completely inserted into the product).
   NOTE: Make sure that the side of the tray that holds the CD/DVD is inserted into the printer first.
2. In HP Photosmart Essential, click the Print tab.
3. Click Printer Settings and then click Advanced to open the printer properties.
4. In the properties, click the Features tab.
5. In Paper Type , select Printable CD 120mm .
6. In Source , select the CD/DVD tray .
7. Save the settings and then again attempt to print on the CD or DVD.

Try this :

Disconnect the printer from the computer.
Turn it off & make sure the CD/DVD tray is closed then turn it back on.

***

Here's generic instruction for you:

If you are receiving an error pertaining to the CD TRAY NOT BEING INSERTED CORRECTLY, please do the following:

Recommendations:
-Don't force the CD/DVD tray into the printer.
-Make sure your printer is powered on, and the output tray is in the upper position.
-Please ensure there is at least 3 inches of space behind the printer, or the CD tray may eject.

Included, are the correct CD/DVD loading instructions. Please follow the instructions below:

CD/DVD LOADING:
1. Ensure the printer is powered on. Remove any paper from the sheet feeder.
2. Push in the paper support extension on the printer, and close the paper support.
3. Push in the output tray extensions, but leave the tray open.
4. Lift the output tray. Place one hand on the top of the printer, and pull up on the output tray until it stops. Lay the tray down in the upper position.
5. Place the CD or DVD into the CD TRAY with the white (or printable) side facing up. Note: To print on small 8cm CDs, please place the small CD ring on the tray first, then place the CD inside the ring.
6. Slide the tray into the tray guides located in the output tray. Push in the guide until the arrow on the tray matches up to the arrow on the tray guide.
7. Press the PAPER button to load the CD/DVD into the printing position. The CD is correctly loaded when the printer's POWER button stops flashing.

General tips for CD and DVD printing:
-Burn data/video/images onto CDs or DVDs before attempting to print on them.
-Do not use thermal-printable or regular CDs or DVDs in the printer.
-Moisture or fingerprints on the printable surface of the CD may cause marks or smearing to appear after printing.
-All printable inkjet media is different. Some surfaces will absorb ink better than others. If output appears banded, faded, or streaky, print a Nozzle Check pattern to confirm that all colors of ink are printing completely. If the ink does not completely dry or smears after 24 hours curing time, you may need to use the Epson Print CD tools to adjust (lower) the print density.
-The only supported resolution for CD/DVD printing is 1440 dpi (aka "Photo")
-Borderless printing and printing on the "inner circle" (plastic around central hole) of CDs is not supported.
-Do not use the "print preview" feature provided by the Epson printer driver as it will only show the image on a blank field and does not offer a clear indicator of where the image will print.
-The Epson Print CD software works best with JPG images and may not import some TIFF images.

Describe what YOU call CD covers? There is an anomaly here. Are you simply printing onto a4 paper for jewel case inserts or do you mean actually printing onto the CD.