I did below solution taken from skype forum and fix to all my device (iphone,ipad2,ipad mini)
This has now been fixed.
When you search for someone to add to your directory, you then add them and a contact request is generated. This contact request states "Please accept me as a contact so we can call and instant message each other." If your contact does not accept this email, then you are unable to initiate a video call, but you can initate a voice call only.
Once they accept, the video becomes available. Simple as that. It is obviously a security feature and I am surprised that the techies at Skype have not been on here to explain the behaviour of their application.
I have this same problem, but it has nothing to do with accepting a contact. I can't video conference with my wife, and we are both using Macs.
Online forums indicate that this is a problem with Skype 6.2 and later versions, and one specifically noted that 6.3 could not videoconference with 2.8. The problem seems to have started with the latest version of Skype. There also may be an even bigger problem with the latest Mac OS. I run Leopard on an iMac, and my wife runs Snow Leopard on a MacBook. They were working perfectly with video until my iMac auto-updated to 6.3. My wife refuses to update from 2.8 for her own reasons.
Does anyone know if Skype is trying to fix this problem?