The most common reason for the videos not loading or skipping, pausing or jumping is that they are not completed loaded. You can pause the video and let them load and then press play. This resolves almost 100% of issues.
If this does not work, there is a problem other than the above, or if there is a specific error message first try using a different device or a different browser. If the problem persists beyond that please contact support with the specific error you are receiving.