I'm attempting to use the Optimisation tool to build a model to solve for the best allocation of various stockpiles of inventory to customers, based on the shelf lives that each customer requires on receipt of the products and the remaining shelf life on each stockpile of inventory. I'm following the steps outlined in the following (very helpful) post.
https://community.alteryx.com/t5/Alteryx-Designer-Knowledge-Base/Tool-Mastery-Optimization/ta-p/306117
Because the number of combinations is large I've decided to use the Sparse matrix approach to the input anchor A. After running the workflow I receive the error shown below.

Because there are 399 variables in my data (in columns), the 'Elements 399...' part of the error message suggests the model doesn't like my input to the 'O' Anchor. I have combed through all of my inputs multiple times and all input types and structures are consistent with those in the example at the above link. Further, I have deliberately inserted a 'dummy' supply option into the model with unlimited stock available to all customers to ensure it's not an invalid solution that's preventing the model from solving.
I simply cannot see anything else that might be wrong. Can anyone tell me where I might find a solution to the above error ?