Hello,
Thank you for contacting Rank Math, and sorry for any inconvenience caused.
5xx errors are usually caused due to server misconfiguration or other server issues.
Can you please share the website error log with us?
Having the error log file will give a clear idea of why this might be happening.
You can follow this guide to enable debugging in WordPress
https://wordpress.org/support/article/debugging-in-wordpress/ or you can get in touch with your web host, they will help you locate the log file.
Looking forward to helping you.
Warning: openssl_sign(): supplied key param cannot be coerced into a private key in /home/site/public_html/wp-content/plugins/fast-indexing-api/vendor/firebase/php-jwt/src/JWT.php on line 237
Fatal error: Uncaught DomainException: OpenSSL unable to sign data in /home/site/public_html/wp-content/plugins/fast-indexing-api/vendor/firebase/php-jwt/src/JWT.php:239 Stack trace: #0 /home/site/public_html/wp-content/plugins/fast-indexing-api/vendor/firebase/php-jwt/src/JWT.php(202): Firebase\JWT\JWT::sign(‘eyJ0eXAiOiJKV1Q…’, ‘—–BEGIN PRIV…’, ‘RS256’) #1 /home/site/public_html/wp-content/plugins/fast-indexing-api/vendor/google/auth/src/OAuth2.php(470): Firebase\JWT\JWT::encode(Array, ‘—–BEGIN PRIV…’, ‘RS256’, NULL) #2 /home/site/public_html/wp-content/plugins/fast-indexing-api/vendor/google/auth/src/OAuth2.php(504): Google\Auth\OAuth2->toJwt() #3 /home/site/public_html/wp-content/plugins/fast-indexing-api/vendor/google/auth/src/OAuth2.php(544): Google\Auth\OAuth2->generateCredentialsRequest() #4 /home/site/public_html/wp-content/plugins/fast-indexing-api/vendor/google/auth/src/Credentials/ServiceAccountCredentials.php(205): Google\Auth\OAuth2->fetchAuthToken(Object(Google\Auth\HttpHa in /home/site/public_html/wp-content/plugins/fast-indexing-api/vendor/firebase/php-jwt/src/JWT.php on line 239
There has been a critical error on your website. Please check your site admin email inbox for instructions.
Hello,
Can you please create a new JSON key and add it to the Instant Indexing settings?
https://rankmath.com/blog/google-indexing-api/#create-new-json-key
Let us know how it goes.
We are here to assist you.
just create and did it again. but nothing changed.
Hello,
The error message, “OpenSSL Unable to sign data” seems to suggest an issue with the SSL certificate, or some other server-side configuration issue with the OpenSSL module. Please get in touch with your hosting provider and see if they have a solution regarding this.
If everything is correct and the issue persists, we might need to take a closer look at the settings. Please edit the first post on this ticket and include your WordPress & FTP logins in the designated Sensitive Data section.
Please do take a complete backup of your website before sharing the information with us.

It is completely secure and only our support staff has access to that section. If you want, you can use the below plugin to generate a temporary login URL to your website and share that with us instead:
https://wordpress.org/plugins/temporary-login-without-password/
You can use the above plugin in conjunction with the WP Security Audit Log to monitor what changes our staff might make on your website (if any):
https://wordpress.org/plugins/wp-security-audit-log/
We really look forward to helping you.
it has been fixed by itself
Hello,
We are super happy that your issue is resolved.
If you have any questions in the future, please feel free to create a new forum topic, and it will be our pleasure to assist you again.
Thank you.