There is a bug in Blackboard that is causing announcements that were originally created in a course that was copied to a new course, to not be sent out via email. This is a standard setting that many course instructors use. If the announcement is created in the current course it should go out via email. As for announcements that were copied over there is a way to send them out.
Click the chevron next to the announcement title and select edit. From here you will need to manually select the box next to “Send a copy of this announcement immediately”:
This will relay the announcements to the other members of the course via email. There is currently no fix for this so unfortunately manual selection is the only way for now.