Do you have a reproducible example?
If dual_status(model) is INFEASIBILITY_CERTIFICATE, then the dual(constraint) is the associated dual ray.
In some cases, even if the problem is unbounded, the solver might not return a dual ray. In this case, the dual status is NO_SOLUTION. You might need to set some solver options, like disabling presolve, in order to force the solver to compute a certificate.