I had lots of problems with this.
Some I could fix some I could not.
1. Make sure the tool you used to create the relationships did what you expected it to do.
One tool I used to do my schema did not update the relationships.
2. Some tools require that the relationship match an existing index.
3. The tool does a good job, but it is not perfect, so check what is generated and see if it is doing what you want, it doesn't allways!!!