Got 403 when use CloudFront

I have done the following:

1. I created an S3 bucket, and uploaded files

2. I created a CDN distribution, and generated an OAC

3. I pasted the OAC policy to the bucket policy

I can't think of any other reason why I get this error now, I access the object as follows:

https://xxxxxxxxx.cloudfront.net/css/styles.css