My website says the certificate has expired - what do I do?

An expired certificate means the digital proof that secures your HTTPS connection has passed its renewal date, so browsers now warn visitors away with a full-page security error. It is urgent but almost always quick to fix:

• The immediate effect - visitors hit a scary warning page and most will not click past it, so the site is effectively down even though it is still running.
• The usual cause - automatic renewal failed or was never set up, and a certificate that should have renewed quietly lapsed.
• The fix - reissue or renew the certificate through your host or certificate provider; many hosts have a one-click renew, and Let’s Encrypt certificates are designed to auto-renew.

Once it is sorted, turn on automatic renewal so the same outage cannot recur in 90 days.