Unable to open stream from new computer



I have 4 servers that I alternate tests on regularly (not at the same time) using the Streaming API. However, when I tried to launch it from a 5th server, having only one connection opened, I get 420 Error Code.

The strange thing is that if I use one of the 4 previous servers, the Streaming API runs just fine (with one already open). Is it possible that my permission has been set to those servers only and nothing else?