The error message you're encountering, indicates that your access to the SharePoint resource is being restricted by Conditional Access policies set within your organization. These policies may require specific conditions to be met, such as device compliance or multi-factor authentication (MFA), which can prevent token issuance when using non-interactive authentication methods.

AADSTS53003: Access has been blocked by Conditional Access policies.

By addressing the Conditional Access policies and potentially using app-only authentication, you should be able to resolve the access issues you're facing.