My IR 6570 feeder only detect A4 paper and not F4/Legal paper and some times misread the paper

question edited for clarity and toss in some CAPS.

It doesn't take A3 Paper and doesn't have a Tray No. 4.
A4R is just A4 in Landscape Mode, half an A3.

What is A4 and A4R?
The "R" indicates that the paper is set in the landscape orientation. Paper that can be set either in the portrait or landscape orientation. Paper that can only be set in the landscape orientation. 8-1/2" × 11" A4, B5. 12" × 18", 11" × 17", 8-1/2" × 14", 8-1/2" × 13", A3W, A3, B4.
Tray Capacity No-collate Mode Tray A: 250 Sheets (Letter, Statement-R, Executive) 125 Sheets (Legal, Letter-R, 11" x 17")

Tray B: 1,300 Sheets (Letter, Statement-R, Executive) 650 Sheets (Legal, Letter-R, 11" x 17") Tray C: 2,450 Sheets (Letter, Executive) 1,700 Sheets (Statement-R) 650 Sheets (Legal, Letter-R, 11" x 17") Collate and Group Mode Tray B: 1,300 Sheets (Letter, Executive) 650 Sheets (Legal, Letter-R, 11" x 17")

Tray C: 1,700 Sheets (Letter, Executive) 650 Sheets (Legal, Letter-R, 11" x 17")

Staple Mode Tray B/C: 1,300 Sheets/100 Sets (Letter, Executive) 650 Sheets/

https://copiersonsale.com/wp-content/uploads/brochures/Canon-imageRUNNER-6570-Brochure.pdf

https://www.google.com/search?q=canon+ir6570+paper+size

Changing Tray Size Settings

https://www.google.com/search?q=canon+ir6570+change+paper+tray+size

..

Please determine what size you are trying to print (A4, Letter, Legal, etc.). The printer is requesting A4 sized paper in the maunal paper feeder becuase either you selected manual feed or the setting for the default try (usually tray 1) is not set to the correct paper size. In your case, make sure the green slide adjustment on tray 1 is set to A4.

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Try to perform a hard reset for service mode .

Loading Paper
1 Adjust the guides to the position for the paper size you are using.
2 Fan the paper well.
Push down the paper lever. Load the paper (with the lever down). Make sure the print side is toward the fax machine and the paper level is stacked below the paper mark. The feeder can hold up to 200 sheets of paper, or up to 10
envelopes.
Acceptable Paper
The FAX/MFC can handle paper that has the following specifications.
But please note that you can receive fax messages only on Letter, Legal and A4 paper. If you use legal or A4, change the Paper Size setting: (Menu/Set, 1, 1.)
Paper Type Paper Size
Cut sheet Letter, A4, Legal, B5, A5, Executive,
Custom size 2.75-8.5 × 5-14 inches (70-216 × 127-356 mm)
Envelopes DL, C5, COM-10, Monarch
Post Card 2.75-8.5 × 5-11 inches (70-216 × 127-279 mm)
Organizer Day-Timer® J, K, L, M 2.75-8.5 × 5-11 inches (70-216 × 127-279 mm)
Labels and Transparencies 2.75-8.5 × 5-14 inches (70-216 × 127-356 mm)

there is a good possibility that the main thermistor and the sub thermistor has gone bad or is dirty. also it might need adjusted to be better placed next to the upper fixing roller.

Load an original in the automatic document feeder (ADF)
You can copy, scan, or fax a single or multiple-page A4, letter, or legal-size document by
placing it in the document feeder tray.
The document feeder tray holds a maximum of 20 sheets of letter or A4-size paper or 15
sheets of legal-size paper.
To send a basic fax from the control panel
1. Load your originals. For additional information, see Load originals.
2. Enter the fax number by using the keypad, press Speed Dial or a one-touch speed
dial button to select a speed dial, or press Redial/Pause to redial the last number
dialed.
TIP: To add a pause in the fax number you are entering, press Redial/Pause,
or press the Symbols (*) button repeatedly, until a dash (-) appears on the display.
3. Press START FAX Black.
If the device detects an original loaded in the automatic document feeder, it
sends the document to the number you entered.
TIP: If the recipient reports issues with the quality of the fax you sent, you can
try changing the resolution or contrast of your fax.

for further refernce check out the online manual
http://h10032.www1.hp.com/ctg/Manual/c01181836.pdf

Don't be mad, but it never hurts to ask if you've checked the following...

• Made sure that the printer has not been set to use legal or A4 paper in tray 1. You can set this through the options listed in the menu map on the printer display.
  
• Have you checked that the Word document is not setup in the "normal.dot" or in the document itself to use A4 or legal as the default paper type.
• Is the small paper resize lever in tray 1 pushed flush against the 8.5x11 paper in the feeder so that it detects properly.

Less obvious...

• Did you make sure that the print properties are not setup with the wrong tray configuration...i.e. listing a duplexer when one is not present, additional trays, or a feeder?

If the answer is that you have done all of this and the issue has not been resolved, I would try looking for obstruction above the primary feeder tray, in the gear assemblies in and around the bottom of the printer and the tray, or around the paper sensor. (a small plastic lever in the front of the tray.

The top-loading sheet feeder accommodates approximately 150 sheets (depending on weight), and the front feeder is good for around 100 sheets. Actual media sizes supported by the main feeder (top-loading) include A4, B5, A5, Letter, Legal, Envelopes (DL size or Commercial 10), 10x15cm(4" x 6"), 10x18cm, 13x18cm, 20x25cm, and Credit Card (54x86mm), while the front feeder is less accommodating with just A4, Letter, and B5.

Does the copier print correctly when copying off the glass? I suspect that the document feeder has been set up to feed other paper sizes eg A4, A4R. Because of the conflict between sizes the copier adjust the image.