Make sure you connect the device with internet.
The tablet can play video on YouTube; it may take a long time to load some video due to the poor connection, but it still play some video. You can try other videos on YouTube.
Data transfer speed and communications range may vary depending on the following conditions:
² Distance between devices
² Presence of obstacles between devices
² Device configuration
² Signal conditions
² Surrounding environment (wall material, etc.)
² Software in use
Supported file format?
Tablet and smart phone work with files of common format. If it doesn’t support some format, you may install some specific apps to open them.
If it doesn’t open at all, it needs restoring the system.