You cannot release the phase &1

What causes this issue?

The status of the project definition forbids you to release phase &V1&.

System Response

The system does not release phase &V1&.

How to fix this error?

Release the project definition first or unlock it.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.