Your internet speed is insufficient for the 1080p bitrate (~10 Mbps). Solution: Run a speed test. If your download speed is below 15 Mbps, lower the quality to 720p (which is still good, but not "Extra"). Alternatively, download the video via Wi-Fi first for offline playback.
This concept treats "Extra Quality" as a distinct feature set that improves upon standard mobile streaming. xvidiocom mobile extra quality
Moving from standard 24 or 30 fps to 60 fps for smoother motion. 2. Technical Requirements for "Extra Quality" Your internet speed is insufficient for the 1080p