What causes a system to just stop providing secondary dial tone right after hitting the 9?
If you dial 9 and any other number it gives secondary dial-tone.
Verified the route pattern to provide secondary dial-tone is checked.
What else causes this?
The only other thing I can think of is in the translation pattern, I built a few:
#01 - speed dial function
*001 - Speed dial function
*002 - Speed dial function