If you are experiencing buffering, the main cause is a slow internet speed. Take note that internet speed varies and is dependent on a variety of factors.
To troubleshoot buffering, first try lowering the video quality. Video quality is largely affected by internet speed (Higher quality = Higher speed needed). So when buffering occurs try the steps below.
1 - Click the gear/cog "⚙️" to open the video settings
2 - Set the quality to 720p and then try to watch the lesson again. (Please note that after changing the video quality, the video will take a little time to render in the new quality setting)
3 - if it is still not working then lower the setting done by one level and try watching the video again.
Below is a table of minimum internet speeds by quality.
You can get an estimate on your internet speeds by using this link https://testmy.net/download.
Please use the latest internet browser version, please avoid using Internet Explorer.
If using chrome, is "hardware acceleration when available" on? if so toggle off.
Try watching the video in incognito mode
If nothing works, attempt reinstalling the browser.
Is the router old? An old router can create a more unstable network.
If using a Macbook, please also have the latest software update.