Most technical issues can be resolved by working through the following steps.
Clear your browser's history, cache, and cookies
If using a mobile device, make sure your screen is rotated to landscape mode so you can see all course content.
Update Adobe Reader to the latest version
Log out and log back in
Check you're entering your correct User ID (it is three letters followed by numbers)
If the issue persists after trying these steps, contact InstaCert and describe what you're seeing.