How do I enable IPv6 in Debian 3CX-SBC?

[minfrin]

We have been supplied with a 3CX SBC install by a consultant which is running on the Debian supplied appliance. The SBC has dual stack IPv4 and IPv6.

Using lsof we can see that the SBS is listening on IPv4, but it does not appear to be listing on IPv6. Is it possible to confirm how we can switch IPv6 on?

3cxsbc 15637 tcxsbc 12u IPv4 89885 0t0 UDP *:sip
3cxsbc 15637 tcxsbc 13u IPv4 89887 0t0 UDP *:20000
3cxsbc 15637 tcxsbc 14u IPv4 89888 0t0 UDP *:20001
3cxsbc 15637 tcxsbc 15u IPv4 89889 0t0 UDP *:20002
3cxsbc 15637 tcxsbc 16u IPv4 89890 0t0 UDP *:20003
3cxsbc 15637 tcxsbc 17u IPv4 89891 0t0 UDP *:20004
3cxsbc 15637 tcxsbc 18u IPv4 89892 0t0 UDP *:20005
3cxsbc 15637 tcxsbc 19u IPv4 89893 0t0 UDP *:20006
3cxsbc 15637 tcxsbc 20u IPv4 89894 0t0 UDP *:20007
3cxsbc 15637 tcxsbc 21u IPv4 89895 0t0 UDP *:20008
3cxsbc 15637 tcxsbc 22u IPv4 89896 0t0 UDP *:20009
3cxsbc 15637 tcxsbc 23u IPv4 89897 0t0 UDP *:20010
3cxsbc 15637 tcxsbc 24u IPv4 89898 0t0 UDP *:isdnlog
3cxsbc 15637 tcxsbc 25u IPv4 89899 0t0 UDP *:vboxd