three blinking dots near toner portal but no error message. can't load toner, print quality is bad

[whitebirch]

I have a Neverstop Laser MFP 1202mw printer.  I put in 2 toner cartridges' it took a lot of force(I thought I was going to break something)  to load but even after putting in two toners the print quality is still terrible.  I am trying to put in another toner cartridge  but the cartridge will not turn.  The three dot symbol flashes orange when I insert a toner cartridge in the portal But the cartridge will not turn.  Only one small light is lite at the display on the front of the printer = There has never been a "+" +2"etc displayed as it is shown in the user materials.  There are no other symbols or error messages.

So I have lots of questions:

1.  What do the three flashing dots mean near the toner portal?

2.  What am I doing wrong trying to load the "Neverstop" toner cartridges (I use only  HP toner)  I have tried ever suggestion found online.

3.  How do I get the print quality acceptable. I have shaken the cartridge inside the printer...

4.  How can HP make such a product that was suppose to be so simple to add toner but turned out to be a big pain in the butt?

[Valsimot]

What is your drum life?

If the drum is near the end of its life the print quality goes poor, you can't load more toner bottles, and the indicator on the printer is blinking.