Need help for manipuling Matrix

I have a MATLAB CODE of Carr download from https://github.com/elliotcarr/Carr2021a. In this programm a couples multispecies in multilayer porous media is solved. Thé programm considers two cases of problem 1- Non-equal retardation factors across layers 2- Non-equal retardation factors across species. The last problem is treated in PROBLEM D in the main programm (multis_multil).My problem is that i would liké to solve thé problem with Non-equal retardations factor across layers and species simultany. In that case the retardation factors in Line 151 must be express as a Matrix. But when i define R as a Matrix, an error appear, the programm doesn't recongnizes R. I have experiments results for that case of problem. Please i need a help in that way. Here attached the following original programm in a rar archives and the modified main programm for my problem

[Torsten]

I suggest contacting the authors of the code.

[Thomas TJOCK-MBAGA]

Thank you very much, I contacted him recently, but he hasn't answered me yet