Hello! If you've landed here, your custom domain on Google App Engine (GAE) is throwing a NET::ERR_CERT_DATE_INVALID error and Google's managed certificate stubbornly refuses to renew itself. Here's what's likely happening and how to fix it. Cloudflare's Proxy In my case, my domain and subdomains are proxied through Cloudflare — including the ones pointing to GAE-hosted sites. If your domain's A and AAAA records are proxied through Cloudflare (the orange cloud), Google cannot see its own IPs when attempting to validate your domain for certificate provisioning. It hits Cloudflare's IPs instead, panics, and gives up with a Certificate activation has failed. DNS records could not be found warning in your Custom Domains tab. So in this scenario, we need to head to Cloudflare dashboard ➡️ back to GAE dashboard ➡️ wait ➡️ finally, Cloudflare dashboard. Head to Cloudflare Dashboard Head to your Cloudflare DNS dashboard and toggle all A a...
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