“Set Baseline for all Tasks” via REST API caused an error. Why?

Summary:

We are trying to baseline financial project plan using the REST API.

It is assumed that the project has never been baselined.

We ran below API.

Set the financial project plan to baseline (REST API for Oracle Fusion Cloud Project Management - Set the financial project plan to baseline)•

But this API returned “400 Bad Request”.

Error Detail：

"You can't baseline the selected tasks because no baseline version exists for the financial project plan. Baseline the project plan and resubmit. (PJO-2205490)"

• Is it correct to use this API?
• If this is correct, why is there an error?

Version (include the version you are using, if applicable):