We are using Jira Software with our Dev´s for a longer time, we implemented an Jira SD customer portal handled by our consultants, if they whant to invite an Dev (via Watcher function) the dev´s are not able to see the issues.
The roles, groups and permissions are filled propperly, the Permission Helper in Jira SD tells everything is OK, ( see picture below) but it doesn´t work as expected.