Hello,
Thank you for contacting Rank Math, and sorry for any inconvenience caused.
The 400 status code indicates that the server was unable to process the request sent.
However, as an initial troubleshooting step, we’ve seen a case in the past where this was related to compatibility between W3 Total Cache plugin and the hosting. Here’s the thread link: https://support.rankmath.com/ticket/instant-indexing-error-undefined-4/
Could you confirm if you’re using the W3 Total Cache plugin? If yes, please try temporarily disabling it and see if it helps.
In any case, please ensure that the admin area of the website is not getting cached by any caching plugin on the website or the server.
You can also get in touch with your web host regarding this and see if they have further insights into the error.
Looking forward to hearing back from you.
Thank you.
Jeremy,
thank you so much for your help. I have deactivated W3 Total Cache plugin and it worked.
Good job, I really appreciate it!
Best,
Alessio
Hello,
We are super happy that this resolved your issue. If you have any other questions in the future, know that we are here to help you.
If you don’t mind me asking, could you please leave us a review (if you haven’t already) on https://wordpress.org/support/plugin/seo-by-rank-math/reviews/#new-post about your overall experience with Rank Math? We appreciate your time and patience.
If you do have another question in the future, please feel free to create a new forum topic, and it will be our pleasure to assist you again.
Thank you.