Delete unused apps, old videos, or clear your cache. Aim for at least 1GB free space for high-quality 1080p downloads.
Low Power Mode (Battery Saver) is the enemy of YouTube Premium downloads. When enabled, the system tells apps, "Stop all background network activity immediately."
Several technical hurdles can leave a video in permanent queue: Connectivity Restrictions : The most common culprit is the "Download over Wi-Fi only"