Hi @Noyon Chandra Das ,
Welcome to Q&A forum!
According to your description and this article, you may have locked yourself out of SharePoint and OneDrive because of a location-based policy.
As you are an admin, follow these steps to unlock the tenant:
- Select Run Tests below, which will populate the diagnostic in the Microsoft 365 Admin Center.
- In the diagnostic form, select the SharePoint Online root URL and then select Run Tests.
- If the test detects that you have a network-based location policy set and you are currently locked out of your tenant, you can choose to disable the policy.
For more details, please refer to:
https://learn.microsoft.com/en-us/sharepoint/control-access-based-on-network-location
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