Certificate has expired

What's going on

Every certificate carries a hard end date, and this one is past it. Clients reject expired certificates outright — there is no override that's safe to recommend.

How to fix it

Renew or reissue the certificate with the issuing CA (with Let's Encrypt / ACME, check why auto-renewal didn't run — the renewal service being stopped is the usual cause). Then install the new certificate AND its intermediate, and restart the service using it. If a renewed certificate still shows as expired, the old one is still being served — check which file the server config actually points at.

New to certificates? Start with the guide: How to read an SSL certificate.