YouTube videos may not play for several common reasons including internet connection issues, browser problems, outdated apps, or device-related issues. If your videos aren't playing, first check your internet connection to ensure it is stable and fast enough, as slow or disconnected internet is a frequent cause. Next, try refreshing the YouTube page or restarting the app/device to clear temporary glitches. Updating your browser or YouTube app and clearing cache and cookies can resolve many playback errors caused by software bugs or corrupted data. On mobile, incorrect device time settings and interfering third-party apps could also cause problems. Additionally, lowering video quality can help if your internet speed is insufficient for high-resolution streams. Occasionally, YouTube itself may have temporary server issues, so checking its status can clarify if the problem is on the platform side. Overall, systematically checking these factors usually resolves the issue of YouTube videos not playing.