Question:
Why some Report Types do not display on the Report View creation page in Vault?
Answer:
By design, Report View cannot be created based on the Report Types with multiple objects that have more than two object relationships.
Example:
If the Report Type contains two object relationships, it can be used in the Report View.

However, if the Report Type contains three object relationships, it cannot be used in the Report View. The Report Type is not displayed on the Report View creation page.

Related Documentation:
N/A