Come on Marshall - how can we help if you provide no info to go on!?!?!?!

The very first thing to check is:
1. Are you generating the correct Reset pulse?

If you are, next check:
2. Are you getting a Presence Pulse from the device?

If you are, next check:
3. Is your software correctly detecting the Presence Pulse?

Other things:

Is it all wired up correctly, with the correct pullup?
If you're using Parasite Power, have you observed the special requirements which apply?