If you are getting an error, you can try these "fixes", in this order, before calling the testing center directly.
1. Make sure your browser is acceptable:
- Mozilla Firefox - version 27 or later
- Google Chrome - version 33 or greater
- Microsoft Internet Explorer on Windows XP - NOT SUPPORTED
- Microsoft Internet Explorer on Windows 7 - version 11 or later
- Opera - version 17 or later
- Apple Safari - version 7 or later
If you have IE 10 or less on Windows 7, the browser supports this new security, but it is turned off by default. To turn it on, Click the Tools menu, then click Internet Options. Click the Advanced tab and scroll down in the checkbox list to find the Security section. Make sure there is a checked box beside Use TLSv1.1 and Use TLSv1.2.
2. Delete your cookies
3. Clear your cache
4. Refresh your browser
5. Try to register on another device