I notice the model you sent as opt.gms in your post is customized to work with GDXMRW. This works as long as you stay in a Matlab world, but now when you move to a larger forum, it becomes a problem. Potential avenues of help or discussion are closed off because your model is not a generic GAMS model - it only works if you’ve got a Matlab system customized to work with GDXMRW.
That is why the GDXMRW Wiki recommends that you write your GAMS model in a generic way - something that works well with GDXMRW and outside of it. There are also examples of this in the Wiki.