SLA BLA Configure

[elementpbx]

I have been trying to configure SLA on Yealink for months and cannot get any help. I use the T28 and T32 and select BLA under Shared Line. I also tried Broadsoft, but nothing seems to work. I see the SLA tag I need to use in each "line" and it works for my Aastra phones, but not the Yealink. Example: DSS Key 1 : Shared Line with Value of B003687D00007L0048_B003687T0048 for Account 1. This works with my Aastra line, but not with Yealink.

Anyone with suggestions? I am using an Asterisk 1.8 back end with Coredial.