ERR_CERT_DATE_INVALID on Shopify
Why it happens on Shopify
Shopify issues and renews the certificate for you, so this almost always means a custom domain whose DNS still points somewhere else — Shopify cannot renew a certificate for a domain it does not control.
The fix on Shopify
In Shopify admin → Settings → Domains, check the domain shows 'Connected' with SSL 'Active'. If the CNAME still points at an old host, repoint it to shops.myshopify.com and wait for the certificate to reissue (usually under an hour).
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
Shopify 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