Find the scope of the problem.
Try another live channel and an on-demand title. If only one source fails, note its exact name and time. If everything fails, check your account status, active-screen allowance and basic internet access before reinstalling.
Compare the network path.
A speed-test number alone does not describe latency or stability. If practical, compare Wi-Fi and Ethernet on the same device. Pause large downloads and check whether other household devices show the same problem.
Check the player and device.
Restart the player and device through their normal controls. Try a supported alternative source resolution. Clearing cache is different from deleting app data, which can remove your saved settings; avoid doing that until you understand the consequences.
Send a useful support report.
Include the device, player version, affected channels, approximate time and checks completed. Do not send passwords or full private playlist addresses. Support can then investigate source or server options for your account.