Help,digium card can not get Hangup singinaling

we use T1 card (T/E410B),using T1 connect with PSTN Switch.
all works well.
if we make a out bounds call to a Cell phone,then voice connection,and then Cellphone hangup.DigiumCard could not get the hangup siginaling.keep the call living for long and long time.
But calls to proper,can get disconnect sininaling.Normally…

anyone meet the issue?
any suggestion? thanks