I installed an original Q3971A toner into the HP 2840 laser printer, However there is still a notice to install cyan catridge. Can you help please

Take the cartridge out and reseat it. If you bought a compatible toner I would order an OEM HP brand toner. These machines don't work well with compatibles.

Q3971A is a colour toner cartridge. Q3964A is an actual toner/drum, not toner alone. So, no, they are not interchangeable as they provide completely different functions.

Read how it works here:

How Laser Printers Work HowStuffWorks

At the following HP web page you will see the Laserjet 2820 and 2840 First Time Setup and Install Page. All the information you will need to know is right there.
http://bit.ly/cJFquP

If you found this information helpful, please give me a big thumbs-up when you rate my answer. Thank you.

kindly remove the the cyan toner and shake it and install it .if it not working then install new cyan toner.

make sure toner is not refilled just remove the toner and shake it and then install it again.

In this case, actually it is not the Black toner that got depleted. Here the message being displayed indicate that one of the color Toner supply need to be replaced as it got depleted and currently the printer is printing in Black and white using the Black toner cartridge.

in this case, to troubleshoot these issues please try performing the following and check for the results.

* 1. Check for the level of the toner cartridges:

a) Check from the HP Toolbox application. Here are the steps to be performed from your PC:

* Access the Toolbox software.
* Select the Status tab.
* Select the Device status option.

Here you can check for the supplies status in terms of the % remaining for each toner cartridges.

b) By checking the supplies status from the printer control panel display.

On the printer display when printer is in Ready mode the supplies status can be checked from the supplies level indicator. Each toner cartridge and the Imaging drum level will be indicated by a bar which varies according to the level of the supplies present.

c) Print the supplies status page from the printer.

* On the printer control panel menu, press Menu .
* Use the (Right Arrow) button to select Reports, and then press Enter .
* Use the (Right Arrow) button to select Supplies Status, and then press Enter .

If any of the color toner cartridges and the Imaging drum have a low supply level replace them with genuine HP print cartridges.

The part numbers of the consumables are as follows:

* Black print cartridge - Q3960A
* Cyan print cartridge - Q3971A
* Magenta print cartridge - Q3973A
* Yellow print cartridge - Q3972A
* Imaging Drum - Q3964A

Need more info.
What are the dates on the toners are they still in date?
Are they original or refills?
Are they Hp or generic?
If there out of date you need to take them back to where you got them from…
If there refills you might find that the printer does not recognize there full & you should try replacing them…
If there not Hp you can’t contact Hp for support because you will find you have voided warranty. But you should try using originals to see if it prints again.

The OEM cartridges have a chip on them. If the aftermarket supplies do not have the right chip, missing a chip, etc., the machine will not recognize. Placing the old cartridge back in without any toner can give off the same message.

Try rebooting the printer without a cartridge in. Then install the cartridge, either one, and see if that helps. If not, wait for the OEM to arrive.

Turn the printer off and turn it back on again and see if happens now.

handle it with the HP logo facing you, then installing it as carefully as you can.
It has chemical toner inside and they do tend to spill .