The most likely reason for this is that the member has industry-specific qualifications selected. If this is the case, then you will not be able to change the industry without either:
- Editing the qualification to fall under multiple industries OR
- Remove the qualification preventing you from changing the industry
- Or you might have a unaccepted character like <> ? in the notes section of their profile
This is an example of what the alert looks like in the members profile:
I