Question on AQA Spec Paper 1

Hi, just done one of the specimen Paper 1s for A-Level, and I don't understand an answer. The question was "Suggest one reason why electron pair repulsion theory cannot be used to predict the shape of the [CoCl4]2- ion" and the mark scheme says "Too many electrons in d sub-shell". Could someone explain this to me please????
Thank you!!!!

Let's imagine we have tetrachloromethane (CCl₄). We already know, just by looking at this molecule, that it will bear a tetrahedral shape as it has 4 bonding pairs and 0 lone pairs. Now let's look at [CoCl₄]^2-. It too has 4 chlorine atoms attached to it... But not in the same way as in tetrachloromethane.

[CoCl₄]^2- has dative covalent bonding, where a lone pair is donated to the metal ion, instead of normal covalent bonding like in tetrachloromethane. In essence, you have 4 lone pairs being donated to Co from the 4 chlorine atoms - how do we know the shape of this molecule, with 4 lone pairs contributing to its bonding, instead of 4 bonding pairs? We don't, and that's where the electron pair repulsion theory (VSEPR, for short) starts to fail.