I just changed all the cartridges in my epson stylus sx12 but still says theyre empty

Are you using compatible ink cartridges? When a compatible cartridge is empty in an Epson printer the printer reports "Cartridge not recognised". This is Epson's way of scaring you into using Epson branded cartridges. Just change the cartridge and it should be OK.

If it's not that issue then maybe the chip on the cartridge is faulty. Again, just change the cartridge.

#1 Wait until you are out of ink. The warning light and ink-low notifications come on well before the ink cartridge is empty, and even if it runs out of ink in the middle of a print, you can replace it then and finish the print with no problem.
#2 Lift the lid of your Epson inkjet printer to expose the ink cartridge replacement button. Make sure you have plenty of light so you can see what you are doing.
#3 Press the ink cartridge replacement button. This will loosen the empty ink cartridges so they can be pulled up and out.
#4 Fill the empty cartridge at an ink-refilling location, or buy a new ink cartridge to replace the empty one.
#5 Insert the new or refilled ink cartridge into the holder with the same orientation as the previous one.
#6 Press the cartridge replacement button to charge the system and close the printer cover. Charging takes about one minute

Thanks

Replacing the ink cartridges
When the ink is empty refer to your lcd panel message to check which one is empty
open the carriage covers
Remove the empty ink cartridge
replace it with your new cartridge

You can get new ink cartridges from here
http://www.inkandmedialtd.co.uk/acatalog/Epson_Stylus_Photo_RX700_Inkjet_Cartridges
or any decent computer stores or computer fair

From older Epsons: If the ink cartridges are empty (red light on), hold the ink switch 3 seconds to move the print head to the left. If they are not empty, hold paper switch until print head moves left. Once you remove a cartridge you can't reuse it, even if there's ink in it according to Epson.

they are proper mardy machines only happy when using original epson cartridges

http://safemanuals.com/user-guide-instructions-owner-manual/EPSON/STYLUS%20SX105-_E

that guide shows how to change the cartridges and no you dont have to wait untill they have run out to change the cartridges

no it cannot. Those multi-colored cartridge system requires that you put in every single color, AND ensure that they are not empty before they will print. Even if all you want is a black and white copy.

That's just ****!!!

I'm assuming you are using originals. I would suggest you taking the cartridges out and re-inserting them. If you are using refilled cartridges and you used the cartridges to almost empty then probably the chip may have short circuited rendering the chip useless. If you bought remanufctured cartridges I suggest you ask them for replacements. This isn't really that high tech but I hope this helps.

Highly possible that the "compatable" cartridges are not really compatable or that Epson has updated software or firmware to keep them from working. Try replacing with Epson cartridges or see if the non-OEM brand seller has a resetting device so the printer sees those cartridges as full.