Hello @Karan Sawhney ,
Thanks for reaching out.
I think you are trying to get access token for Bing Ads API, please correct me if that's not a case in above sceanrio also could you please confirm account type which is being used? ( work/school OR MSA account? )
I was able to regenerate the auth token by using refresh_token as per this link without any issue so I would recommend you to try this PowerShell way, if that works for you then I guess this issue more on module that you are using to get access token.
I had seen this similar issue when you try getting auth token through Python modules and issue got resolved by updating BingAds Python module update.
Please let me know how that goes. Thanks
------
Please "Accept the answer" if the information helped you. This will help us and others in the community as well.