Have you encountered the problem when you were making a call, it's automatically dropped in about 30 seconds after it connected?
If the answer is yes, what's your next step? Try making more calls to verify the problem and then call the Carrier or PBX vendor to help you to fix the problem? What if you are in an emergency and can't wait for queueing for the limited technical support?
If you have already equipped with the knowledge, you can troubleshoot and even fix the problem yourself. This video will show you how to check if the NAT settings on the Yeastar S-Series VoIP PBX is incorrect or if the ALG setting on the router is incorrect. If these two methods can’t solve your problem, visit http://support.yeastar.com and contact our technical support team by submitting a ticket or starting an online chat.
Here are some related online documents you are looking for:
How to Configure PBX NAT settings: https://help.yeastar.com/en/s-series/topic/nat.html
PBX NAT Settings Understanding: https://support.yeastar.com/hc/en-us/articles/360041265853-understand-the-pbx-nat-settings
How to resolve the 30 seconds hangup problem: https://support.yeastar.com/hc/en-us/articles/360020908914-call-hangs-up-at-30-seconds
How to analyze the 30 seconds hangup problem: https://support.yeastar.com/hc/en-us/articles/360040792774-how-to-analyze-the-30-seconds-hangup-problem-
ALG Settings on the router samples: https://support.yeastar.com/hc/en-us/articles/360020911174-the-router-settings-relevant-with-one-way-audio-30-seconds-call-hang-up-issue