Hello,
I see you’re encountering an API Error: HTTP 400 on your website. This error typically occurs when the server cannot process the request due to a client error.
To resolve this issue, you can check a few common reasons and solutions outlined in our knowledge base article here. Some common causes include website maintenance, website status issues, API timeouts, API requests blocked by the firewall, or hosting the website locally.
If you’re still facing difficulties after following the suggestions in the article, please feel free to reply here, and a human agent from our support team will assist you further.
Thank you for reaching out with your concern.
Sources:
Why Am I Getting "API Error: HTTP 400" Error » Rank Math
How to Fix Failed to Submit Post to the Bing URL Submission API Error » 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 193.138.6.5 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.