Please keep in mind that holding a certification doesn't immediately qualify an SPC to instruct that course - they must still complete the course delivery enablement learning plan, including the exam, before they are eligible to be added as a trainer for a class.
That being said, there are some additional reasons why you may not be able to add an instructor to a course.
If you cannot add an instructor, please work with them to verify that their certification is in good standing and that they have completed all required elements of the trainer enablement for the correct version of the course. (For example: Being enabled in the 5.0 version of the course does not enable you to teach the 5.1 or 6.0 version of the course.)
Instructors cannot be scheduled for two courses that overlap any dates. If any of the days of either of the courses overlap, they will only be able to be added to one and they will need to decide which course to be added to.
At this time, it's not possible to add an instructor after a roster has been uploaded, or the course has been completed. If the roster has been uploaded, but you haven't taught the course yet, then you will need to delete all students from the roster before you can add another instructor. If students have already been uploaded into the class roster and marked as attended, or the class has already occurred, we recommend opening a case through support.scaledagile.com for help adding additional instructors.