Amazon SP API Authorization issue

I’m using the python module to access Amazon’s SP API, I followed all of the instructions and I got it working at first, the authorization was successful, but 3 weeks later I come back to my code and suddenly the authorization is failing for an unknown reason.

This is the error message I got:

raise exception(error, headers=res.headers) sp_api.base.exceptions.SellingApiForbiddenException: [{'message': 'Access to requested resource is denied.', 'code': 'Unauthorized', 'details': ''}] 

I tried getting a new refresh token but that didn’t help, I also changed the IAM ARN from user ARN to role ARN but that didn’t help either, why would my authorization suddenly stop working?

Thank you for the help.