Set the AMP ASSIGN setting to 9.1CH and then set the FLOOR LAYOUT setting to 5CH. Now set the HEIGHT SPEAKER setting to HEIGHT and 4CH.
Also ensure that the SURR. HEIGHT speaker configuration is set to NONE and that the REAR HEIGHT SPEAKERS are actuallu engaged within the REAR HEIGHT setting. If left set to the SURR. HEIGHT option then the rear most height speakers will not be engaged when portraying Atmos. You need to be using the REAR HEIGHT option and not the SURROUND HEIGHT option! This will engage all 9 speakers with Auro 3D, Atmos or DTS:X.