Well, I seem to get the global scenario.
- You're developing in Delphi, while in Delphi there's no known integration API to get the token as in C#.
- You're trying to get the token via postman then apply the token in Delphi to import pbix file to Power BI Serivce.
So
- I don't know how postman works to get that token, that token looks wrong.
- Try to get the token via C# getting-started-for-dotnet-import (you're requesting token via postman, did you have any approach to integrate postman with Delphi?) and write the token somewhere, maybe in a text file. In Delphi import the pbi file with the token in text file. The token can expire, so you would have to re-run the C# to get a new one.
Or as I sugguested before, check Call C# dll from Delphi. - The registered app is a native client app, cilentid is enough to get the token.