Changing settings through rest api

I am trying to change the administrator settings using REST API. I want to add custom CSS to layout by sending the following JSON payload to /api/v1/settings/theme-custom-css

  "_id": "theme-custom-css",
  "value": "\n[data-id='video-message'] {\n\tcursor: pointer;\n}\n\n\n\n[data-id='start-discussion'] {\n\tcursor: pointer;\n}\n\n\n[data-id='file-upload'] {\n\tcursor: pointer;\n}\n\n\n.rc-message-box__send {\n\tcursor: pointer; \n}"

The problem is that I get the following response form the endpoint:

  "success": false,
  "error": "TOTP Required [totp-required]",
  "errorType": "totp-required",
  "details": {
    "method": "password",
    "codeGenerated": false,
    "availableMethods":  [  ]

What am I getting totp-required? And how can I fix this?

Needed to Disable Account > Two Factor Authentication > Enforce Password Fallback.

Based on documentation, one can also do the following:
pass these headers with each request
X-2fa-code: SHA256_of_your_password
X-2fa-method: your_password