converge

In Pick up group:-

1) when try to pick up the call by call-pick button first then there is no talk path, Its dead air

2) when first took recevier off-hook & then press call-pick button , there is no problem. ( I can recevie the call & talk)

whereas it suppose to work in first way also ,pls assist to find reason of not working.

S8700, CM 3, Ip phone 4620, G650