WHY CAN'T I SEE IT?  Yep, I've been trying AMC3, 12162 H, 4347.  I scan it and only get a radio station, no TV.  I then deleted the TP altogether, blind-scanned the sat.  It found the TP again, shows a sig quality of 41, but no MT PBS.  
Here's the list of all TV sigs that the 3688 finds...