SoftwarePassport/Armadillo is a solution to lock your software application, so if you're using that to lock the program you're selling as a download, then we host a keygen script that will generate keys which can unlock your software. Contact Silicon Realms for any advice you may require as to which signature level and encryption template you should be using, as we don't actually know much about how their keygen script works, aside from hosting it on our server for you to use.
If you're not using SoftwarePassport or Armadillo to lock your program, then the only other use of that keygen would be to generate a random serial, so that would be sent to you and the buyer afterwards, for you to do as you wish. Whatever serial is generated for each sale should be included in the buyer's thank-you email automatically; I can't see anyplace where the email message would say "Please contact us to get the code(s) for Sniff."
I was unable to run a free checkout test on your "URL Test Product" because you have Shipping enabled in that product's settings. If you could disable that for us, we can run a test checkout and see what the email we get looks like and look for any errors in our server logs if something seems amiss.
EDIT: I just tried your keygen URL in a test product of my own, and indeed, that didn't generate a code and instead only emailed a message to "Please contact us to get the code(s) for Send Codes: Generated." However, I changed the parameter arm_level=-1 and obtained a code just fine, so perhaps there is something amiss with your keygen URL, maybe the encryption template (arm_keytext) phrase is too short for the level you specified?