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Fail to open a meeting with pade

I am new to openfire and pade and try to set up a IM system to be used by my collegues.
Chatting and sending pictures via pade are ok. Very thankful to openfire community for providing such a powerful open source IM.
But can't start a video meeting.
This is the description of the problem.
1. https://domain_name:7443/ofmeet/testconf could be open in chrome browser.
2. After user name and password was entered, I can see live video from camera. Everything seems ok.  
3. But after I did so in the second computer, an error message is shown: Unfortunately, something went wrong. We're trying to fix this. Reconnecting in.....
I guess the two computers can't connect with jitsi, but I wonder what did I miss?
Any suggestion would be great. thanks a lot.

openfire : 4.7.2
pade: 1.6.3

this is the error message: