static website content does not update

I have a static website hosted on s3 using cloudfront. Domain hosted on Route53. My initial deployment worked fine and the app served at the domain. But when I upload changes to s3, the modified files do not serve. Files on s3 are definitely updating. So it appears that cloudfront is caching and serving the old files.

I found these articles: https://repost.aws/questions/QUfh2n4klfRHuzKpGJsjOkNA/old-s3-content-being-served-help and https://stackoverflow.com/questions/30154461/aws-cloudfront-not-updating-on-update-of-files-in-s3

Have tried a) creating an invalidation in my cloudfront distribution, b) creating a cache policy with 0 min ttl / 10 max ttl and applied to my cloudfront default behavior, c) adding Cache-Control headers to my s3 objects with max-age=1 (by updating the metadata on all the files). None of these approaches correct the problem.

FWIW, I have another distro set up on a different domain - exactly the same set up. Never had any issues with that one. The only difference is that the domain for that one is hosted by a third party, not Route53...

Any thoughts would be appreciated.