Kindly make sure you are using good internet connection. Data connections (mobile viewing) may not be sufficient to stream the videos seamlessly.
Here are additional tips:
1) Refresh your web browser window:
press command + R
2) If refreshing the page still does not help you stream the videos, try using a different browser (Chrome, Firefox, Safari, Edge). Log in to your program once again.
3) Clear cache and restart program:
How to clear cache:
On your computer, open Chrome.
At the top right, click More.
Click More tools Clear browsing data.
At the top, choose a time range. To delete everything, select All time.
Next to "Cookies and other site data" and "Cached images and files," check the boxes.
Click Clear data.
From the History menu, select Clear Recent History.
If the menu bar is hidden, press Alt to make it visible.
From the Time range to clear: drop-down menu, select the desired range; to clear your entire cache, select Everything.
Next to "Details", click the down arrow to choose which elements of the history to clear; to clear your entire cache, select all items.
Click Clear Now.