It seems like HTTP Requests are not working if they are inside OnPluginStart() and the server is still starting... if I reload the plugin after the server has fully loaded, using "sm plugins reload <pluginName>", then the HTTP Request retrieves the wanted data just fine. It has something to do with the server yet loading when an HTTP Request is called.
I didn't want to use a timer to fix it... Do you know if it's fixable or if there's an alternative to OnPluginStart(), some ServerLoaded() callback?