So, this unhelpful error message is still plaguing me. A little more detail, in case someone wants to weigh in:
I had though maybe it was a scaling issue, as the product of many of these variables will potentially be quite small (on the order of 10^-7). The presence of the positive constants are my code replacing very small values in the matrix with 1, so I both adjusted this threshold (realizing that this may invalidate the results, but results I can interpret in light of this approximation are better than the nothing I am getting) and I rescaled the remaining terms... No joy, however.
As far as I can tell, the product of log-affine expressions and positive constants should be allowed by the code in cvx\prod but it simply fails without explanation.
A few more questions:
Is the fact that the error message "Shouldn't be here" indicative of a set of conditions which cause prod to fail? Is this a bug in the code the developer just never bothered to deal with or properly document? Am I wrong in believing that this type of product is in fact valid?
I'm beginning to question reality at this point, and if you're reading this, please feel free to reply with a non-answer, an opinion, or anything. Given the other questions on this particular cvx function which have not reply from the dev, I'm starting to think this topic is auto-/shadow-banned.