Hello,
I’m sorry to hear that you are still facing the 400 error while trying to whitelist Rank Math in Cloudflare. It seems like you have followed the instructions provided in our article on how to whitelist Rank Math in Cloudflare.
Since you are still encountering the issue, it might be helpful to ensure that you have correctly added the IP addresses mentioned in the Cloudflare WAF and custom page rules. Double-check that the IP addresses are entered accurately and that there are no typos.
If the issue persists after verifying the IP addresses, you may want to reach out to our support team directly by clicking here. Our team will be able to assist you further in resolving this matter.
Thank you for your understanding, and we appreciate your patience as we work to resolve this issue for you.
Sources:
Why Am I Getting "API Error: HTTP 400" Error » Rank Math
How to Whitelist Rank Math in Cloudflare » Rank Math
Hello,
Thank you for contacting us and sorry for any inconvenience that might have been caused due to that.
Please get in touch with your host and make sure the IP 46.30.211.100 and the user-agent RankMathApi/2.0.2; https://rankmath.com are whitelisted on your firewall.
Once done, please head over to your WordPress Dashboard > Rank Math > Status & Tools > Database Tools and click the Clear SEO Analysis and Remove Transients buttons to flush the SEO Analysis cache.

Please clear your website and any server-level caching on your site before doing the SEO analysis again.
For more details on this issue, please check this URL: https://rankmath.com/kb/api-http-400-error/
Let us know how it goes. Looking forward to helping you.
Thank you.
Hello,
Since we did not hear back from you for 15 days, we are assuming that you found the solution. We are closing this support ticket.
If you still need assistance or any other help, please feel free to open a new support ticket, and we will be more than happy to assist.
Thank you.