The moonshine anomaly cohomology conjecture

Let $\mathbb M$ denote the Monster group, and let $H^3(\mathbb M,\mathrm U(1))$ be its third cohomology group with coefficients in $\mathrm U(1)$. Moonshine anomaly cohomology conjecture. There is an isomorphism

$$H^3(\mathbb M,\mathrm U(1))\cong\mathbb Z_{24}.$$

This is proposed as an analogue of the theorem identifying $H^3(\mathrm{Co}_0,\mathrm U(1))$ with $\mathbb Z_{24}$. The authors explicitly provide little evidence for it, and the source gives no resolution.