Lloyd Keen (thanks Lloyd) recently reported a bug with COS and Siblings. Basically, COS breaks the sibling support. We have created a fix for this in -619 but it isn't completely seamless. We've had to create a new entry point in extensions.conf. Now, this is no problem if you don't have any siblings. Bit of a pain if you do. Here's the deal....
You will first need to install -619 (it's available on the download site now). Then, you can either delete and recreate all of your existing sibling trunks.. OR, ...you can change the
context= entry in each existing sibling trunk definition.
Click on the edit button for the trunk and change the
context entry in the right-hand edit window. It will look like this...
type=user
secret=whatever
context=internal
Change it to this
type=user
secret=whatever
context=priv_sibling
Now, you DONT need to do this if you aren't running or intending to run COS, OR, if you don't run Siblings. It is only necessary if you wish to run BOTH.
You
can run pre -619 siblings
without COS alongside modified -619 systems.
Sorry everyone, this is a complete PITA, we don't usually get it this wrong.

Kinds Regards
S