Treat playback as a chain: source, network, device, player and account. Change one variable at a time so you can see what helped.
Find the scope of the problem
Try another channel and an on-demand item if available. Check whether ordinary internet services work on the same television. One affected source needs a different investigation from every app failing.
Compare the connection
Use Ethernet if supported, or move closer to the router. Pause large downloads and compare another normal viewing time. If you already use a VPN, compare its effect where permitted; it is not a universal playback fix.
Check the device and account
Restart the player, install official updates and confirm the account’s expiry and simultaneous connections. Try a lower available resolution. Record the error, device, player version and time before contacting support.