[Freeswitch-users] Freeswitch+sangoma a101 can not hear ring back tone

hello:I install fw and sangoma A101 card with sangoma isdn. after few days, caller can not hear the ring back tone, but the voice worked. the hardware is ok, compare with normal status, the alert message lost. how do i set that to enforce to send alert message? Best regards, James.zhu Doing asterisk/PRI/ss7/dahdi, linux, asterisk/sangoma cards, recording device, VOIP gateway. website: www.hiastar.com