we already have several threads about Siri the answer very well could be in one of those. here is one https://forums.macrumors.com/threads/1299353/ also it's better to ask in those threads rather then start a new one. many of us aren't using Spire.
This might sound silly, but it tripped me up at first with my iPhone 4S.
On the iPhone 4S anyway, you have to turn on Siri - the home button doesn't do it automatically.
Settings --> General --> Siri --> On/Off
Not sure how it works with the jailbreak/port, but just a possible suggestion.
Get a 4S.