HP 2550 LASER JET

Hello
I have this printer hp 2550 laser jet which has the cartridge's leds blinking warning that there is no tonner enough since this morning.
The problem is that at the beginning there were just two of the leds blinking (for two of the four cartridges). After replacing the two corresponding cartridges with new ones, then now not only two but the four leds corresponding to the four cartridges (black, blue, red, yellow) are blinking warning that there is no tonner enough in any of the cartridges.
Is there anything I am missing?
Thanks

I wonder if this is related to HP control-freakery about third party toners.

I have the 2600n and noticed that when I replaced exhausted cartridges with half used ones from another HP, my printer's readout started claiming that these were not HP catridges, though they obviously were, and the correct model. Something to do with counting the number of copies remaining. Fortunately there was a menu option to turn off that that annoyance.

If you have had the impertinence to insert non HP cartridges or to remove and reinsert the same cartridge, look for a menu option to tell the printer to shut up and do its job.

Or I would ring HP and give them an earful for wasting your time. Firms like this tend to forget who's boss unless told regularly.

The four print-cartridge lights are blinking, and the printer stops printing.
The print cartridges are empty or missing. The printer cannot detect the print
cartridges correctly or The E-label reader might be faulty.
1. Replace any non-HP print cartridges with HP print cartridges.
2. Reinsert or replace the print cartridges.
3. If the print-cartridge lights are still blinking but the Attention light is not on, turn the printer off and then back on.
4. If the problem persists, repeat steps 1 through 3 with sets of print cartridges until the error is resolved.
5. If the problem persists, replace the print-cartridge Elabel reader, which is located
on the pressure assembly of the print-cartridge carousel