The playlist does not respond

Check that the link or server is typed correctly.
Test the playlist on another device: if it does not open there either, talk to whoever supplies the playlist.
In Settings → Sources, use Test again: the TV gives the exact reason.

A channel does not open or the picture freezes

When the channel has other versions, the player switches to the next one by itself and lets you know.
Weak Wi-Fi near the TV is the usual cause: a network cable fixes it most of the time.
If only one channel fails, the problem is usually at its source, not on the TV.

MetroMedia shows a notice on screen and comes back by itself when the internet returns. The license keeps working for up to 30 days without internet.

My media needs the MetroMedia License. The window shows the 7-day trial or the QR code to pay, plus the TV ID for support.

Send an email with your TV ID (Settings → License). With it, we know which TV and app version it is without asking for any of your data.