First of all, please check that you have a stable internet connection, ideally via WiFi. If this doesn't resolve it, it could be that your browser/device is out of date or doesn't support the video format. Try using a different browser (e.g. Google Chrome, Firefox) or device.
If this still doesn't fix it, please send us an email to email@example.com with the following details:
Which video are you trying to play?
What device (e.g. iPhone, Android phone, laptop) are you using?
What browser (e.g. Safari, Google Chrome, Internet Explorer) are you using?
We will then get in touch with you to try and help.