YouTube videos not playing can be caused by several common issues:

• Internet Connection Problems: Slow, unstable, or disconnected internet is the most frequent cause. Video streaming requires a good connection; even if your page loads, insufficient speed especially for HD or 4K videos can prevent playback.
• Browser Issues: Glitches, outdated browser versions, or corrupted cache and cookies can stop videos from playing. Refreshing the page, clearing cache, disabling extensions, trying another browser, or updating the browser often fixes this.
• App or Device Problems: On mobile, using an outdated YouTube app, corrupted cache data, or device settings like incorrect date and time can cause playback errors.
• YouTube Server or Bug Issues: Occasionally, YouTube experiences outages or bugs affecting video playback, requiring waiting for a fix.

Common fixes include checking your network, refreshing the video or page, lowering video quality, updating or reinstalling the YouTube app or browser, clearing cache, restarting the device, and verifying the YouTube server status. If issues persist after these steps, it could be due to a temporary YouTube platform problem.

In summary, check your internet connection, refresh or change video quality, update your browser or app, clear caches, and restart your device. Confirm YouTube's server is up. These actions resolve most video playback problems.