I can use internet and mail. My internet has no problem.
In addition, I can't use online help because of the same reason. It seems like camtasia misunderstands or makes an error.
Then, what should I do? Please tell me.
First I tried many of the help links including registration and all successfully connected. (Perhaps the registration server was down and is now working again.) I am using CS8 but don't think there should be a difference in this issue.
Searching for "Camtasia can't connect to the internet" and "camtasia unable to connect to register" and ignored the common problems of anti-virus, firewall, behind proxy server, etc. The common solution often required contacting customer support which sometimes resulted in repairing a registry entry.
So, that is what I would suggest if you are still unable to register and assuming you can connect to www.TechSmith.com outside Camtasia.
Thanks to you, I found that I can't connect to www.TechSmith.com by my PC(window10).
On the other hand, I can go to www.TechSmith.com by my another PC(windows8) or iPhone.
So now I understand that the problem is in my PC(window10).
Then, I've tried firewall, anti-virus, off, but they doesn't work.
Searching other way.
For the fun of it open a command prompt with admin rights and try the following command.
That will, uh, flush the DNS cache and might, just might, clear up an issue.
Try accessing the TechSmith website again. If it works (lucky!) stop reading.
I can't think of a way one computer, these days, would be blocked from a specific site without an action being taken. The only one that might be easy to happen is in the browser security section. In IE that is Tools > Internet Options > tab Security. Check the "Restricted" zone. The Hosts file is another simple way to block a site but that requires modifying a file.
Do you have an alternate browser installed? If so, see if the other browser can access it. (Hint: Since Camtasia can't access it the issue is not likely browser specific so don't install anything to try.)
I really don't know how to proceed if the above doesn't work.
I doubt this could happen today but... A long time ago, shortly after we got DSL (before FIOS), we had two computers in the same room connected to the same router. I was taking an on-line class and one computer could always connect and mine (of course) could rarely connect.
A TRACERT to the website showed both computers took different routes and the route mine took had a single server which was almost always offline. Today, I would change the DNS servers and hope that worked. However, today I doubt this could happen. Still, if it recurs this info might help. If not, well, you just wasted another 2 minutes. :D