what project permissions are needed to allow for stakeholders to be added on JSM?

I have one JSM project that isn't allowing me to add users that have been assigned with the Product role of "stakeholder" but on another JSM project I can add those people into the stakeholder field. I can't figure out what the difference is that is causing it to not work on one but does work on another.... Are there permissions, customer settings, and/or portal settings requirements in order to allow users that are "stakeholders" in Product roles?