“Due to the 2020.02.29 CAA Rechecking Bug 5.6k, we unfortunately need to revoke many Let’s Encrypt TLS/SSL certificates.”
To check if your website has been affected please check the following link: https://checkhost.unboundtest.com
If your affected the following warning will be shown:
Read the bug announcement here: https://community.letsencrypt.org/t/2020-02-29-caa-rechecking-bug/114591
Read the revocation announcement: https://community.letsencrypt.org/t/revoking-certain-certificates-on-march-4/114864