Hi @Omkar I assume you've seen this thread, but if not it provides a good range of solutions for your issue: https://stackoverflow.com/questions/43332236/bad-request-400-when-making-api-call-to-microsoft-graph
Without any more information this is tricky to solve. Can you please email your query to jahami@microsoft.com? I can look it over and see if I can spot the issue.
Best,
James