Help with 3CX Phone System PBX Edition V.15.5.5

[vortuna]

I am having some issue with SIP Trunks. Some times outbound call made it out success but some times failed From extentions to sip skype connect (sip.skype.com)

Error msgs: Call or Registration to 628138331xxxx@(Ln.10000@SkypeConnect) has failed. 0.0.0.0 replied: 408 Request Timeout; internal

Here what I have done so far with no luck to fix this issue:
1. Check skype connect status

SIP user successfully registered at sip.skype.com
Last registration: July 17, 2017 at 15:34 GMT

3CX PBX - SIP Trunks - conected

2. Firewall Check - Firewall test OK
3. Disabled windows firewall.
4. Open inbound ec2 secgroup for all TCP and UDP for test perpose.

Note: 3CX PBX installed on AWS EC2, Windows_Server-2016-English-Full-Base-2017.06.14

 

[leejor]

Intermittent problems like this can be real tricky to troubleshoot as you can't replicate each time.

This may very well be a network problem, but might require tools such as Wireshark, to track down the cause.

Was this working for a long period in the past? Did the problems seem to start after "something" was changed, hardware, firmware, provider, etc.?

 

[vortuna]

This 3cx pbx is fresh new one just install it couple days ago.
with the cloud provider I do not have any access to ISP or router there are only security group for inbound and out bound, and its has been opened for all tcp and udp.

Any idea what I am missing in here? I also have talked with skype connect support but still no luck.