Hi Ronald,
You can run the autoconfig-buttons-freepbx.sh config script in the linux console and check its output. A Trunk button should list every channel on the pri with "Channel=" directives, something like:
[ZAP/1]
type=trunk
label=My Pri
channel=ZAP/2
channel=ZAP/3
..
If your modification was done in half, you might get something like:
[ZAP/1]
type=trunk
label=My Pri
channel=DAHDI/2[/color:3js302xk]
And that will fail to monitor ZAP/2.
I am just guessing, but that might be the issue you are having.
Best regards,
--
Nicolás