CaptureContext Generate Failed: Target Origin[0] can't use http protocol unless the host is locahost

[shist]

When I generate capture context on my local env by using Flex V2 for customer website server, we set target origin to  "http://localhost:xxxx" and it works correctly.

But for our payment testing server, we set target origin to "http://pay.localhost:xxxx" and call "generateCaptureContext"

 function. It return an error below:

stdClass Object
(
    [correlationId] => df3a4c0c-6779-4d57-b92f-2fe5abab49ba
    [details] => Array
        (
            [0] => stdClass Object
                (
                    [location] => targetOrigins
                    [message] => Target Origin[0] cannot use http protocol unless the host is localhost
                )

        )

    [message] => One or more validation errors occurred
    [reason] => VALIDATION_ERROR
)

 My question is: how can we set sub domain for the test when we have to test on multiple servers ?