Create challenge reqestfrom lichess bot not working

step to reproduce:

• open Postman or any other REST client
  do exactly like https://lichess.org/api#operation/challengeCreate :
  [POST] https://lichess.org/api/challenge/{username}
  (change {username} by the great value)
• add header: "Content-Type": "application/x-www-form-urlencoded"
  don't forget to add header "Authorization": "Bearer XXXYYYZZZ..." (api token with all privileges)
  execute the POST request and you will see in json "destUser": null

The "rated" parameter is required, do you have that?

yes I have "rated" parameter set to true

I think sincerly that the problem comes from backend. Try to reproduce and you will see

Right, I reproduced the issue. Thanks for the report!