No incoming call

[Live71]

I am new to 3CX but I was able to set up with SIP to dial out the call but there is no incoming call goes to the phone. The Phone is Fanvil H2u-V2. When test call is made it goes to vm directly. It seems shows webpage dial showing there is incoming call, but it remains only a second. What did I miss here? The call log shows " Unanswered 00:00:02 00:00:00 0.00 No answer, forwarded to VMail (2xxx0)"