Http requrest not working with basic auth

I am implementing the Payment method by using the API of smart2pay fully API based. But the API not seems to work in appGyver, although I am providing correct basic auth string. API with basic auth string is working in Postman but not working in Appgyver. Please help.
Authorization: Basic (Auth string Base64 encoded)

web inspector:

  1. Request URL:
  2. Request Method:OPTIONS
  3. Status Code:405 Method Not Allowed
  4. Remote Address:************(hidden)
  5. Referrer Policy:no-referrer-when-downgrade

Hi there

From the information you’ve provided it appears that the api endpoint is rejecting the OPTIONS request. There could be a few reasons this happens, so my suggestion is you contact the support for the api vendor to resolve this issue.

You can read more on what the OPTIONS request is here