If you can't open a resource file, make sure the file you want to open has downloaded completely. The amount of time a file takes to download will depend on how big the file is and the speed of your internet connection.
You also need to ensure that you have the correct software installed for the type of file you are attempting to open. Some of the uploaded files will have been created for specific applications and interactive whiteboards. There are some viewers available, or alternatively there are limited trial versions that you can install. Find out more about various file types and the software required to open them here.