Why they cannot keep things simple is beyond any sense!

One of my printers was a Canon that used ink cartridges.

It decided to give up the ghost, and demand to be serviced.

I decided it was time to retire it, as I have very little ink cartridges left for it anyway, and they do cost.

Decided to go and buy a new one.

At the store, they did not have the model I wanted - it is superseded.

I have one of these, which has ink tanks, which makes it much cheaper to operate, so thought of getting the same model.

No.

Outdated and brand new ones are in the showroom.

The salesman proceeded to try to sell me an EPSON printer, despite me asking for a Canon.

I convinced him that I was NOT going to buy an EPSON - had problems with these before, and did not want anything to do with them.

Bought myself a brand new printer, took it home, and installed it as instructed.

Printed a sample page and all went well.

Then tried to print a Word document.

The printer refused to print it, showing "PAPER SIZE DOES NOT MATCH PRINTER SETTINGS"

Went through all the settings on the computer, made sure everything says A4.

Went to the printer display, made sure everything says A4.

Again, the bloody thing refused to print, showing the same message??

Thought of rebooting everything, which in lots of cases works.

Both computer and printer were turned off and on again.

No luck!

What the hell is going on??

Went to the printer display, and went through all the menus.

Guess what?

A setting there to warn the user of the mismatch of the paper size settings, decided by the computer SMART brain.

I turn that off.

There was no mismatch between the settings on both the printer and the computer.

But, the warning setting is decided by the SMART PRINTER BRAIN!!

I got rid of my inkjet printers a long time ago.
I bought a laser printer. The cartridge is supposed to print 700 pages. I'm happy.

Seed, this happened to me also. Rather than creating a long post, go to the internet.
Google Canon troubleshooting
Enter your model number
They will guide you through the "paper size" setup.
Not too complicated but somewhat involved.
You can usually find a video covering the problem.

We all need an 8 year old in the house to help us with these things :-)