I've just joined PE and after flying on non towered airports and talking to myself

When I contacted the KSBP tower on 124.0 just before entering its airspace nobody answered so I turned around back to L52 :/
- I was connected to PE
- I did setup my Xplane "Contact ATC" button
- I did have the correct COMM 1 frequency set
- I did check my Windows recording setting and made sure the mic is picking my voice.
What did I miss? How can I do a comm check to be sure that my PE setup works?
A more general question: how do I know if a given tower is online (has a controller) or not?
thanks!
cheers,
Tex