We've looked through the forum posts related to the same problem, it turns out, that this happens due to the security settings of your hosting server. You need to contact your hosting provider and ask them to take a look at your access and error logs for this URL /video/add/index/ and 404 error code and find out an exact reason of forbidden.
It will be also great for the community if you get back to us with the hosting reply, so we could use it in the future.
Thanks in advance.