My Epson WF-7710 display indicates Paper out in Cassette 1. Even though there is plenty of paper in the cassette.

It is possible that your Epson WF-7820 is experiencing a paper jam or a misalignment of the paper cassette. If the paper cassette is not correctly inserted into the printer, the printer will display an error message that tells you to insert the cassette correctly. To resolve this issue, make sure the paper cassette is correctly inserted and that any paper jams are cleared. If the issue persists, try resetting the printer by unplugging it and then plugging it back in. If the error message still appears, contact Epson support for further assistance.
Loading Paper in Cassette 1 (Upper Cassette)
https://files.support.epson.com/docid/cpd3/cpd39348/Source/Printers/Source/Paper_Loading/Tasks/XP800/loading_paper_upper_xp800.htmlfaq-207896 ' SPT_C11CB58201 ' Epson WorkForce WF-7520 ...
https://epson.com/faq/SPT_C11CB58201~faq-207896?faq_cat=faq-topFaqsWF-3820 Series User's Guide
https://files.support.epson.com/docid/cpd5/cpd58812.pdf

If you have problems feeding paper, try these solutions:

·Make sure the paper cassette is inserted in a proper way.

·Check the paper size and type settings properly you loaded.

·If paper does not feed correctly, remove and reload it in the cassette and adjust the edge guides. Make sure the paper stack is not above the tab on the edge guides inside the cassette.

·If multiple pages feed at once, remove the paper, fan the edges to separate the sheets, and reload it.
·Do not load more than the recommended number of sheets.

·Make sure your paper meets the specifications for your product.

·If paper jams when you print on both sides of the paper, try loading fewer sheets.

·If too many pages are fed when you are performing manual 2-sided printing, remove all other paper from the cassette before reloading the paper.

I hope your problem will be resolved. If you need any help, you can directly contact Epson printer experts through Free Live Chat.

The switch inside that makesxeither an electrical connection orca mechanical one tells the printer that the paper tray is home loaded and awaiting commands is not being activated by the tray
The switch has become faulty overtime and needs,a replacement
The bit on the tray that pushes the tray loaded switch has broken off the tray is missing the switch or a wiring fault has developed
And the switch has no power so it still can't see the tray even if it is loaded thus error paper tray missing continuously is being displayed

change paper size in print settings

If its not a setting problem, it may not be communicating with your computer properly, try turning it off, wait a little while and turn it back on, if that doesn't work delete your printer off your computer and re install it, Is it the default printer on your computer? some times if you run more than one printer from your computer there's a conflict which can make it behave in weird and wonderful ways.

Have you tried setting the paper size for each cassette, then setting the printer to Auto instead of selecting the cassette?

I was also stuck with this error message for a while. It turned out to be a 4x6 photo paper got stuck in back in a place that was not easily visible. I had to detach the double-sided paper module from the back, tilt the printer on its side and reach in with fingers and pliers to pull it out. The error message was correct, that something was blocking the cassette tray even though you could push the tray all the way in!

Look at the feed rollers.
If you pull the paper cassette out and look into the now exposed area, you will see two rollers in the machine, just above where the roller in the front of the paper cassette was positioned.
If these rollers are worn, they will not grab the paper and pull it out of the paper cassette. This will cause the machine to think that there is a paper jam, even though no paper is found in the machine because the machine is looking for the paper via a paper path sensor in the front of the machine, just a few inches up from the paper cassette.
Look closely at these rollers... they should have a "rough" surface. If any of them are smooth, you will have to replace them.
There are two blue hub rollers and one white roller.
Part #'s:
Blue: RM1-0037-000CN (Qty.2)
White: RM1-0036-000CN (Qty.1)

Hi ...

Most of the time this problem comes when the paper is not loaded correctly. Follow the below instructions to load papers to the cassette and I am sure this will resolve your problem. I will keep monitoring your responce and if required, i'll look for a work arround.

Follow this procedure to load paper / envelope in the cassette:

1. Pull out the cassette from the machine.
   
   
   
   
2. Remove the cover from the cassette.
   
   
3. Fan out the sheets of paper so that they do not stick together.
   
   
4. Align the edges of the paper.
   
   
   
   
5. If the cassette is not yet extended, use your thumb to press the tab (indicated by the pink circular outline) and release the latch.
   
   
6. After the latch is released, remove your thumb from the tab. Then extend the cassette until a click is heard.
   
   
   
   
7. Load paper on the upper-right corner of the cassette with the print side facing down.
   
   Note:
   * Since the Credit Card sized paper, Canon Photo Stickers, and Legal sized paper cannot be fed from the cassette, load them in the auto sheet feeder (ASF).
   * When loading A5 or larger sized paper (nonstandard-size paper: 203mm / 8inches or more in length), extend the cassette by pinching the tab.
   
   
   
8. Grasp the paper guide (A) and align it to the long edge of the envelope stack (2). Align the front edge of the paper stack in the same way (3).
   
   
   
   
9. Close the lid and push the cassette all the way into the printer.
   
   
10. Press the <Open> button and pull out the extension completely.
    
    
11. Press the <Feed Switch> button to turn on the Cassette light.
    
    
    
    *MP500 shown.
    
    Note:
    If the Auto Sheet Feeder lamp lights, press the Feed Switch button to light the Cassette lamp.
    If the Cassette lamp does not light even after pressing the Feed Switch button, Paper Source in the printer driver may be set to the setting other than the Feed Switch button.
    

Loading on envelopes
Paper Type
Precaution
Envelope (DL / #10 )
Set paper with the flap closed.

1. Press down firmly on the edges of the envelopes to make the folds crisp. Also, press firmly on the area that corresponds to the edges of the back flap.
   
   
2. Remove any curling by holding the edges diagonally and bending them gently.
   
   
   
   
3. If the edges of the envelope are inflated or are curling, place the envelope on a flat surface. With a pen, press down while moving it from the center toward the edges of the envelope.
   
   
4. Ensure that no curl or puff exceeds 1/8 in. (3 mm).
   
   
5. Load envelopes in the cassette with the print side facing down and the flap towards the left.
   
   
   
   
6. Close the lid and push the cassette all the way into the printer.
   
   
7. Press the <Open> button and pull out the extension completely.
   
   
8. Press the <Feed Switch> button to turn on the Cassette light.
   
   
   
   Note:
   If the Auto Sheet Feeder lamp lights, press the Feed Switch button to light the Cassette lamp.
   If the Cassette lamp does not light even after pressing the Feed Switch button, Paper Source in the printer driver may be set to the setting other than the Feed Switch button.
   

Don't forget to vote if this helps ... Cheers :)