On December 8th the group operating the free NEOS service announced on Twitter that from January this year users are required to provide a valid email address for all job submissions to NEOS.
Unfortunately, this change affects GAMS users who submit NEOS jobs via Studio. We are working on resolving this issue with the coming release of GAMS 34.
As a workaround you can submit jobs via Kestrel
instead of directly via GAMS Studio, and provide an option file
kestrel.opt. Provide your email in this file with the keyword
$echo email email@example.com > kestrel.opt
$echo kestrel_solver cplex >> kestrel.opt
mymodel.optfile = 1;
solve mymodel using lp minimizing obj;
This solution might not work in all circumstances though, because with Kestrel the GAMS execution phase happens locally, so you might run into license related limitations. For more information you can read this blog article. .