There are basically two options, which could hinder you your backend from accessing the new platform.
a) You use an IP whitelist, but did not update to our new IP addresses
With the switch to our new platform our IP addresses have changed. You need to whitelist the new IP addresses in order to still be able to accept requests from our platform.
The new IP addresses are:
PROD: 126.96.36.199 and 188.8.131.52
QA: 184.108.40.206 and 220.127.116.11
b) You are sending requests to our old IP address, instead of using the hostname
Since the IP address has changed, please change the request address to our hostname https://service.hubject.com