https://scotthelme.co.uk/lets-encrypt-old-root-expiration/ On 30th September 2021, the root certificate that Let's Encrypt are currently using, the IdentTrust DST Root CA X3 certificate, will expire. You may or may not need to do anything about this Root CA expiring, but I'm betting a few things will probably break on that day so here's what you need to know! Anything that requires a secure connection to a particular server can stop working. Streaming platforms such as Netflix, Stan, Binge and 7plus require users to have this secure connection. It can also affect any website that requires a user to login, such as email inboxes and banking sites.