When you installed a new toner cartridge TN 730 & TN 760, but the printer still getting the error message " replace toner". 

It is because the reset gear of the toner is not in the correct position, if it is not in correct position it con not reset toner counter and the printer con not recognize it is a new cartridge. 

You can relocate the gear and reinstall the toner cartridge to reset the toner counter.  

Procedure to relocate the reset gear on the toner cartridge.

1. turn the internal shaft gear clockwise to the position 1, the D shape washer should be in the dot line zone.

2. turn the reset gear clockwise to the correct position.

Each compatible cartridge have a marker mark the correct position of the reset gear.