What is Buffering?

Buffering is the pause while a player downloads enough video ahead of playback to continue smoothly. Constant buffering means the connection can't keep up with the stream's bitrate.

Fixes in order: restart the streaming device, move it to 5 GHz Wi-Fi or ethernet, lower the app's playback quality, and test at different times of day (evening slowdowns point to network congestion, not your equipment).