Hmmm, there can be a few reasons why the loading of the names fails. First you might have disabled the generation of names inside the GAMS code. One can do this by setting mymodel.dictfile=0; before the solve statement (https://www.gams.com/latest/docs/userguides/mccarl/model_attributes_mainly_used_b.htm). Another reason could be that you run out of memory when GAMS tries to load the names. If you can’t figure this out I suggest you post the entire model plus log files to this forum.
-Michael