As of today, the Screencast.com share option in older versions of Snagit will no longer work. So, if you are on version 13 or earlier, that option is no longer supported. If you are on the older version, you should have been notified of this via an email we sent out.
If you are running a newer version of Snagit and the share option to SC.com is not working, please let me know.
You are still able to upload to SC.com.. you just have to do it manually. Here is a support article that explains this: