Payment request with cloud LG fails with 403 error (works fine with local LG)

We are testing a web-application which allows online donations via card payment. We have the following request in the script, which works fine when we use the local LG, but we get 403 error when using a cloud LG:
https://testsecureacceptance.cybersource.com/pay

Please suggest if we have to make any changes anywhere in the script or settings.

Thanks.