Check whether the issue is local
Try another app or website on the same network. If everything is slow, investigate the connection first. If only one app has a problem, check the app and service status.
Give your connection a stronger signal
Move closer to the router or use Ethernet on a compatible device. Busy networks and weak Wi-Fi can interrupt playback, especially when several people are using the connection.
Restart one thing at a time
Close and reopen the app, then restart the streaming device if needed. Avoid changing several settings at once, so you can tell which step helped.
Collect useful information
Write down the time, error text, device model, app version, and whether other streams work. Do not include passwords when preparing a support request.