Dear All ,

I have an customer have NEC SL1000 and they bought new piece of Grandstream GAC2500 as audio conference this device able to connect 7 attendees on one conference call , the problem is when the dial first number and wait till answer then add it to conference then take second line to dial second number after dialing process the grandstream give us 403 forbidden and conference call failed

I feel it from SL1000 side

SL1000 firmware R6.0

Any help plesase