Grey print output rather than black on a new Laserjet 700 M712

We have a brand new A3 printer which is printing dark grey rather than black.

The unit is running the originally supplied HP 14A (CF214A) toner cartridge and has printed less than 40 pages.

The toner status still shows as 100%

We have set the Density to 5, the Resolution to ProRes 1200, REt to On and Economode to off.

This printer is to be used for printing graphics and without being able to print a solid black, it isn't fit for the intended purpose.

We have tried PCL and Postscript drivers.

The issue is evident whether we are printing on 80gsm white paper or laser printer transparency film.

I'm hoping someone may be able to offer a solution.

Thank you.