SLA Implementation using SIP Trunk

Good day everyone:

I am trying to get SLA implemented in my office for testing purposes and to learn more about it. We are using Trixbox, which is a flavor of Asterisk, with both Linksys SPA942 phones and Aastra 57ict phones. All of our incoming lines are SIP trunks hosted with Teliax with NO ZAP cards or FXO boards.

Based on reading a ton of posts and PDF documents, this is what I have so far:

*************SLA.CONF**********
[general]
attemptcallerid=no
ringtimeout=30
barge=no
hold=open

[line1]
type=trunk
device=SIP/zone
autocontext=line1

; ---- Station Declarations ------------
[401]
type=station
device=SIP/401
autocontext=sla_stations
ringtimeout=10
ringdelay=10
hold=private
trunk=line1

[402]
type=station
device=SIP/402
autocontext=sla_stations
ringtimeout=10
ringdelay=10
hold=private
trunk=line1
*******End SLA.CONF*******

*******Begin Extensions_custom.conf*******
[macro-slaline]
exten => s,1,SLATrunk(${ARG1})
exten => s,n,Goto(s-${SLATRUNK_STATUS}|1)
exten => s-FAILURE,1,Voicemail(1234|u)
exten => s-UNANSWERED,1,Voicemail(1234|u)

[line1]
exten => s,1,Macro(slaline|line1)

[line1_outbound]
exten => disa,1,Disa(no-password|line1_outbound)
exten => _XXXX,1,Dial(SIP/\${EXTEN})
exten => _1NXXNXXXXXX,1,Dial(Zap/1/${EXTEN})

[sla_stations]
exten => 401,1,SLAStation(401)
exten => 401_line1,hint,SLA:401_line1
exten => 401_line1,1,SLAStation(401_line1)
exten => 402,1,SLAStation(402)
exten => 402_line1,hint,SLA:402_line1
exten => 402_line1,1,SLAStation(402_line1)
******End Extensions_custom.con*******

******Begin Sip_custom.conf******
;--------------Zone VOIP Trunk-------------------
[zone]
type=peer
host=den.teliax.net

;--------------SIP Devices-----------------------
[401]
type=friend
host=dynamic
secret=1234
context=sla_stations
qualify=yes

[402]
type=friend
host=dynamic
secret=1234
context=sla_stations
qualify=yes
******End Sip_custom.conf******

Right now I can connect a line on either phone to Ext 401 or 402 but not Ext 401_line1 or 402_line1 as indicated in several PDF files.

What am I missing to get to this step?

Thanks!