According to this FAQ https://knowledge.ariba.com/AC_Content_Details_Page/1,,161_127731,00.html:
It is possible that the site parameter 'Application.ACM.RestrictCopyProjectToOwner' is set to 'Yes.' This will restrict the projects that one can copy to those in which he/she has an ownership role. This parameter can be turned off if the need for users to copy projects that they do not own is prevalent. A Designated Support Contact will need to submit a Service Request to have this parameter value changed by and Ariba Customer Support representative.
Another reason for not being able to copy a project can be attributed to the status of the template from which it was created. If the template from which a project or workspace was created is inactive, that project or workspace cannot be copied. The template will need to be reactivated before a user is able to copy the project or workspace.
Also, if the project template has:
Access Control = Owner Only
A condition that restricts creation of projects with this template to a particular user or group of users
Then, only the users that have access to use that template can copy a project that uses the template. This would be the users listed in that condition.
Note: Creating a new version of a template makes projects that use an earlier version of the template unavailable for copy. You must create a new version to remove conditions or access controls, so you would be able to fix the issue moving forward, but any projects created with this condition in place or access control can only be copied by the users in the condition or by the owners.
Hope that helps!