Hello @kellydk,
I am glad that this solves your problem, but please do not include the from-internal context in the from-internal-custom context. It is already included and it might cause a loop.
Another thing, you will have to escape the semi-colon in your Call-Info link.
It should look like this:
[from-internal-custom]
exten => 2007/2008,1,Log(NOTICE,GDS3710 is calling to extension ${EXTEN})
same => n,GoSub(func-set-sipheader,s,1(Call-Info,<https://IP_of_GDS3710:443/capture/8001>\;purpose=GDS-view))
Thank you,
Daniel Friedman
Trixton LTD.