Eddy,
IMPORTANT UPDATE: I'm doing several tests here. Please read it.
We know that IP is being used by several websites because it's a shared hosting from LOCAWEB, we can't change it.. However we found an important pattern.
flip.siteseguro.ws/flip/ <-- IT's OUR website, responding to 187.45.240.51, IT'S BLOCKED.
trajano.siteseguro.ws <-- IT'S NOT OUR WEBSITE, it's a third one, responding to 186.202.153.105, IT'S BLOCKED
gerenciadorwebfinancebr.siteseguro.ws <-- ALSO, IT'S NOT OUR WEBSITE, responding to 191.252.51.12, ITS BLOCKED
Whats the pattern? All blocked websites has suffix "siteseguro.ws". Whats the explanation?
As I could check the blocked websites has "siteseguro.ws" as domain suffix. Every website has several additional domains that are blocked too, so, this explain why eflip.com.br/flip/ is blocked among other ones.
Does it make sense for you?