Integration not working in Appian but working in POSTMAN (Appian could not find a DNS address)

While trying to call an API, we are getting an the below error:

success: false

result: null (Null)

error: Integration

Error title: "The external system could not be found"

message: "Appian could not find a DNS address for https://eis-apim.deviq-uat.work.iqvia.com"

The call to this API worked fine in POSTMAN and the connected system with the credentials got authorised successfully as well.

Is there some kind of setting with the network that needs to be changed to allow calling this integration endpoint?