ERR_CERT_DATE_INVALID on WordPress
Why it happens on WordPress
Managed WordPress hosts renew certificates on their own schedule, and a domain moved between hosts often keeps DNS pointing at the old host whose certificate has since lapsed.
The fix on WordPress
Confirm the A record points at the current host, then trigger a certificate reissue in the host's dashboard. Do not install a certificate manually on managed hosting — it will be overwritten.
Is ERR_CERT_DATE_INVALID happening on your domain?
The SSL checker returns the exact notAfter date and days remaining for the hostname, which immediately separates 'genuinely expired' from 'your clock is wrong'.
Free, no signup. Runs from outside your network, which is the only way to tell a server fault from a local one.
If that didn't fix it
WordPress has its own failure mode, but ERR_CERT_DATE_INVALID has a wider set of causes that apply everywhere. The most common one overall is: the certificate expired and auto-renewal silently stopped.
All causes and fixes for ERR_CERT_DATE_INVALID