That might be an issue about "documenter"…. and is not only for your repo. Other Julia optimisation documentation also have that problem.
For instance, this equation fails to render: It is under quick tutorial then constrained optimization
[\begin{align*} \underset{ \mathbf{x} }{\text{minimize}} \ & \tfrac{1}{2} | \mathbf{x} * \mathbf{h} - \mathbf{y} |^2 \ \text{subject to} \ & \mathbf{x} \geq 0 \end{align*}]
Newbie here, cannot help much more, good luck!