Cannot activate the Split object button in Vertier software

An object must be split in several objects for different colors with a second extruder. Therefore it is necessary in the Vertier program to press the little cog icon next to the nozzle selection.
A menu appears, but for me it is not possible to activate the Split Object button.
What’s going wrong?

More then likely the model was not designed for multi colors

Thanks,
I’ll design an object myself to verify this.