PJClientCallableException: EnterpriseProjectTypeInvalidCreatePDPUid error when creating EPT

public void CreateEnterpriseProjectType(Guid eptGuid, string eptName, string eptDescription)
    {
        ProjectContext pwaContext = new ProjectContext("http://serverName/pwaName");
        pwaContext.Credentials = new NetworkCredential("adminUsername", "adminPassword", "domainName");

        EnterpriseProjectTypeCreationInformation eptData = new EnterpriseProjectTypeCreationInformation();

        eptData.Id = eptGuid;
        eptData.Name = eptName;
        eptData.Description = eptDescription;
        eptData.IsDefault = false;
        eptData.IsManaged = true;
        eptData.WorkspaceTemplateName = "PROJECTSITE#0";
        eptData.ProjectPlanTemplateId = Guid.Empty;
        eptData.WorkflowAssociationId = Guid.Empty;

        // Get the maximum order of the existing EPTs and increment by 1 in order to use an order that does not already exist
        eptData.Order = Convert.ToInt32(Database.GetValue("SELECT MAX(ENTERPRISE_PROJECT_TYPE_ORDER) FROM [ProjectWebApp].[pub].[MSP_ENTERPRISE_PROJECT_TYPES]")) + 1;

        pwaContext.Load(pwaContext.ProjectDetailPages);
        pwaContext.ExecuteQuery();
        List<ProjectDetailPageCreationInformation> projectDetailPages = new List<ProjectDetailPageCreationInformation>() {new ProjectDetailPageCreationInformation() { Id = pwaContext.ProjectDetailPages[1].Id, IsCreate = true }};
        eptData.ProjectDetailPages = projectDetailPages;

pwaContext.Load(pwaContext.EnterpriseProjectTypes);
        pwaContext.ExecuteQuery();
        pwaContext.EnterpriseProjectTypes.Add(eptData);
        pwaContext.EnterpriseProjectTypes.Update();
        pwaContext.ExecuteQuery();
    }

When executing the code above, I get the following error:

Microsoft.SharePoint.Client.ServerException : PJClientCallableException: EnterpriseProjectTypeInvalidCreatePDPUid
EnterpriseProjectTypeInvalidCreatePDPUid
column = PDP_UID

Any ideas on what I'm doing wrong? The PDP Id is valid, I checked it in Debug mode.