Hi @Pankaj Kalambe and welcome to the Community!
You actually answered your own question: a sprint belongs to a specific board. Since you are seeing your sprint on board B, it is perfectly normal that it is not on Board A, as that is not where it was created.
Quite simply: you only get board reports on the board where you created a sprint originally. So if you use multiple boards to track your work, make sure in the future to create your sprints from the same board consistently.
Hope this explains!
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