R is the log of a linear fractional. Have you shown the problem is convex? If there were only one term in the objective, you could eliminate the log` and get an “equivalent” problem having the same argmax, and solve as a linear fractional problem. But that won’t work because your objective is the sum of log terms.
Also, you need to declare R as an expression of he correct dimensions. Although the program encountered an error before it would have encountered an error from the incorrect expression declaration.