I was Performing an upgrade for a client recently when I encountered this error.  In the past when I received this error it was usually the result of my incorrectly typing the name of one of the four Project Server databases incorrectly.  This time, however, that was not the case.  Error message and resolution are below:

Error Messages

Failed to provision site test with error: Microsoft.Office.Project.Server.Administration.ProvisionException: Failed to provision databases. —> Microsoft.Office.Project.Server.Administration.ProvisionException: Non project schema.
   at Microsoft.Office.Project.Server.Administration.PsiServiceApplication.EnsureDatabases(ProjectProvisionSettings provset, SPSite pwaSite, String adminName, String adminEmail, ProjectDatabaseStateType& originalDatabaseState, Guid& adminGuid)
   — End of inner exception stack trace —
   at Microsoft.Office.Project.Server.Administration.PsiServiceApplication.EnsureDatabases(ProjectProvisionSettings provset, SPSite pwaSite, String adminName, String adminEmail, ProjectDatabaseStateType& originalDatabaseState, Guid& adminGuid)
   at Microsoft.Office.Project.Server.Administration.PsiServiceApplication.CreateSite(ProjectProvisionSettings provset)

Provisioning instance’: One or more of the databases already contains schema. When editing or creating a Project Server instance, you may specify:
* Four databases that do not exist
* Four existing, blank databases
* Four existing Project Server databases of the same version from the same installation.
Combinations of blank, new, and existing databases are not allowed.

Resolution

In this specific case the following required extended properties were removed from the four project server databases

  • ProjectCollectionGuid 
  • ProjectDatabaseType

Once we added these back in the upgrade was successful