Getting TLS handshake error on integration with 3rd party api

Hi I am getting below error when I integrated application API which is hosted on AWS EC2 instance. At AWS instance I am getting below error. When that api is accessed from postman, then it is working perfectly fine. So its for sure that something needs to be set up at wix (client side code).

Error -

http: TLS handshake error from remote error: tls: unknown certificate