We have TWINNING set up with no problem. Presence button to turn twinning off and on, cell number as EHDU, using a SIP trunk so it actually works.
When calling internal (extension to extension) - everything works as advertised - BOTH cell and desk extension works fine.
HOWEVER - when transferring an external call to an extension (or getting to an extension via the auto attendant during lunch/after hours) the cell phone does not ring (just the internal extension).
External calls are on copper LS trunks - the twinned call to cell goes out on SIP.
Any ideas?