Can Scan A5 size duplex

Sounds like you are trying to convince the machine to print a document on to paper half the size required without telling the machine to reduce or scale the document to fit the target paper

what do you mean with A5 paper? do you want to scan an A5 sized picture, or put a picture on A5 sized paper?

At the bottom of the printer you will find the paper cassette. Pull the handle and the cassette will slide out. Eventualy you will need to ajust the size of the paper.

first remove all paper trays and inspect for paper behind the tray area and inside the machine
second verify if the paper trays are set to the correct paper sizes this is easy just look at the screen under paper trays and all trays should tell you what they are set to

solution clean the paper sensor and service the two solenoid that's the problem inside the printer

This is from Canon's web site...

Ten flashes:The Cassette is not installed properly/Cannot perform duplex printing

• When loading from the Cassette, install the Cassette properly and press the RESUME/CANCEL button.
• When performing automatic duplex printing, the size of paper may not be compatible with automatic duplex printing. The sizes of media suitable for auto duplex printing are A3, Regal, 11" x 17" (Tabloid), B4, A4, Letter, 10" x 12", 8" x 10", B5, and A5". Make sure that the size of the paper loaded in the printer is correct. Pressing the RESUME/CANCEL button will eject the paper and restart printing from the front side of the next paper. The reverse side of the ejected sheet will not be printed.

Make sure the paper type and size in both trays are the same. If you are using letter size for both trays, make sure the settings in tray 1 and 2 are the same. If the settings are the same and it still fails to grab from the full tray change the engine settings in diag mode. Hope this helps but if you need more assistance, leave a comment and I'll get back to it. Thanks.

Hi. You need to do tray linking. When one linked tray is empty, paper feeds from the next linked tray. The size and type settings for all trays must be set from the Paper Menu. To set the paper type or size:
1. On the home screen, touch Menu button
2. Touch Paper Menu
3. Touch Paper Size/Type.
Note: To link the multipurpose feeder, Configure MP must be set to Cassette in order for MP Feeder Size or MP
Feeder Type to appear as a menu item.
4. Touch the right or left arrows to select the same size paper from all paper sources to be linked.
5. Touch the right or left arrows to select the same type paper from all paper sources to be linked.
Note: When the Size and Type settings are the same for any trays, the trays are automatically linked.
6. Touch Submit.
Submitting changes appears.
7. Touch Home to return to the home screen.
Hope this helps.

The iP4300 manual says this for 10 flashes "
The size of paper may not be compatible with automatic duplex printing. The sizes of media suitable for auto duplex printing are A4, Letter, A5, and 5" x 7". Make sure that the size of the paper loaded in the printer is correct. Pressing the RESUME/CANCEL button will eject the paper and restart printing from the front side of the next paper. The reverse side of the ejected sheet will not be printed." Hope this helps

Media paper weight: is 20lb or 75gsm.
Media type: card stock, envelopes, Glossy paper, Paper Labels, Plain Paper, Transparent.
Media size: A3, A4, A5, Banner up to 11.69"x36", Executive, JIS-B4, JIS-B5, Ledger, Letter, legal, Super Tabloid, B5, C4, C5 DL, 7 3/4 9, 10 Envelopes.
demension is in inches, you need to convert it to centermeter.