Tell the user to follow these steps: 

1. Close your browser completely. The process is different on all devices, but for example, on a Samsung Galaxy S4, hold your home button until this screen appears: 

2. Tap the X button on the far right side of the screen to close your browser. 

3. Reopen your browser. If your course still doesn't show up, uninstall your browser app and reinstall it, if possible.