Replaced K toner and machine is telling me there

If shakingthe toner doesn't work and moving the blue “handle thing” back to the unlocked and then locked position Try the following:
Try switching slots cartridge with drum with another cartridge and drum in the printer once and print a test page. Then switch them back. This actually worked for me. Information given to me by a OKI tech. It forces the printer to reset the ink amt. setting.

There are sensors along the inside right wall that tell the unit if there is a K cartridge inserted. Usually what happens is that due to a toner spill, the sensor LED is covered with toner and or is bad . Hence it does not see the K cartridge. This happens mostly with the black or K cartridge. Get some compressed air and lightly shoot some into the hole that corresponds to the K cardtridge. Only in the hole, do not spray the air anywhere else in the printer.
If this does not clear it up, you would need to replaced the sensor board which is held in with 12 springs!
If I could be of further assistance, let me know. If this helps or solves the issue, please rate it.
Thanks, Joe

On your printer front, press Enter key 3 times. A Menu Map will print. Under USAGE MENU check the K Drum. It shows the life left on the drum. You can also verify the amount of toner left in your cartridges. Hope this helps. If not, call Oki Support 1-800 654-3282.. They are very helpful at no charge.