I’m using a Yaesu FTM-400 connected to my M2 LEO pack.

A few questions for those that are more familiar:

I sent CQ SAT FN20 as my message, is this appropriate or is there a bette format?

I expected to receive an automated reply from RS0ISS, but I did not.  Any idea as to why not?

I received a direct message from another operator, to which I replied.  His was the only message that I decoded although I heard many other transmissions.  Any idea why I only decoded one?

I went to aprs.net and I see all of the messages there, including mine.  

Wondering if there are any resources for learning about this more, especially using the FTM400 APRS and satellite.

Thanks for the help!