It seems that your process cannot run because your robot is not having credentials. It seems you chose an attended robot, not an unattended one with Windows Credentials.
Before playing and testing the API calls in Postman, check how it is looking the correct API call in the back-end. (right-click on the Processes tab page and go to Inspect → Network → look how it looks the /odata/Jobs/UiPath.Server.Configuration.OData.StartJobs request in Headers and the JSON Payload)
Example:
Let us know if this helped.
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