ERR_SSL_CERTIFICATE on Make.com: SSL certificate error. Root cause: The SSL/TLS certificate presented by the target server failed validation. Common causes include an expired certificate, a self-signed certificate not trusted by the automation platform, a certificate hostname mismatch, or an incomplete certificate chain. Step 1: Check the certificate in a browser. Navigate to the target URL in Chrome or Firefox. Click the padlock icon → Certificate → Details. Check the "Valid to" date (is it expired?), the "Subject" field (does the hostname match the URL you are calling?), and the "Issuer" (is it a trusted CA or self-signed?). Step 2: Renew an expired certificate. If the certificate has expired, renew it through your certificate authority (Let's Encrypt, DigiCert, etc.). For Let's Encrypt, run certbot renew on the server. After renewal, restart the web server (nginx: sudo nginx -s reload, Apache: sudo apachectl graceful) and verify the new expiry date in the browser. Step 3: Fix a hostname mismatch. If the certificate is issued for "www.example.com" but you are calling "api.example.com", the certificate does not cover the subdomain. You need either a wildcard certificate (*.example.com) or a SAN certificate that explicitly includes the API subdomain. Contact your certificate authority to reissue. Step 4: Install the full certificate chain. SSL errors in automation tools often occur because the server is only sending the leaf certificate, not the full chain including intermediate certificates. In your web server config, ensure you are using the "fullchain.pem" file (Let's Encrypt) or the bundle file provided by your CA, not just the domain certificate alone. Step 5: For Make.com: disable SSL verification as a temporary workaround. In Make.com, open the HTTP module that is failing. In the advanced settings, there is a "Verify SSL certificates" toggle. Disable this only for internal or development endpoints — never for production APIs handling real data. This is a diagnostic step to confirm SSL is the cause, not a permanent fix.