I'm trying to put a new toner cartridge in my Lanier LD430c. I followed the instructions, but the printer still tells me that the black toner is empty and I have to add toner.

SOURCE: Toner Empty Message won't go off

check that the toner is inserted correctly, reboot print.

SOURCE: "toner empty" problem

The samsung sf 5100 toner cartridge has a .05 Amps fuse in it. This gets blowed when you switch on the machine.This is used to reset the page counter and also to inform the machine that you have inserted a new toner. Now this recycled cartriges will not have this fuse and this is the reason why your machine shows TONER EMTY message! If you dont get the same rating fuse, put any fuse of the same size, insert the toner, close the door and just switch on the power and switch off immediately. Then take out the Toner cartridge and remove the fuse. Now your cartridge is ready for use.

SOURCE: How to reset Black Toner Empty Message on 2430Dl

There are many problems like that and its not recommended to change toner from one printer to another.
but you should try: put the old toner (emty) in again, then turn off the printer, change toner and turn on printer again.
if thats not helping, then maybe you have a old FW so you can try to update the firmware.

SOURCE: Toner Cartridge empty

does the display come up as "toner empty x"? what is the last character after the toner empty ?

where x is:
c=cyan= 6,600 pages
m=magenta=6,600 pages
y=yellow=6,600 pages
k=black=10,000 pages

SOURCE: cannot remove toner cartridge

There is a manual removal option. Open the front cover. Then the top. Remove the drum. Close the front cover. (leave the top open). Move the toner housing unit so the required toner is accessable from the back. Remove.

Replace drum. Restart printer. The housing unit shoud rotate the empty spot to the front so you can insert the new toner.

Good luck.