We have been working on this issue with our vendor for months to no avail. We have an FXT with a PRI. All 23 channels on the PRI should be 2 way. However, if more than 8 outbound calls are placed, all phones get a "No Lines Available" message.
The vendor has assured me that the trunk group is larger than 8 trunks.
Here's what we've done:
*PRI testing with both carrier & CPE on site.
*Swapped the PRI card
*Swapped the PRI card slot
*Collected/analyzed errors
*Had a 2nd vendor come in and examine the programming.
*Escalated to Comdial.

Right now, we're talking about trying to budget for a whole new PBX. Any thoughts would be appreciated.

1. Check how many lines are programmed in your outbound line group. You may have multiple line groups and it's not stepping between them. I would turn off ARS and try direct dialing and see if the problem is a switch or carrier problem.

2. Button map all 23 B channels on a 24 button set and check that they are all in service.

Yep, what RBF said.

Sometimes it is thge little thing snot checked that are the solutions.

RBF has some great things to try. Start there, and let us know what you find.

If the suggested procedures don't shed any light on your problem, you can send the database to us for analysis. Comdial will no longer provide any support on the FXT-sorry to say.