Updated
Buffering is almost always the path between your device and the router, or a 4K stream on a line that cannot hold it. Change those two things before you assume the subscription is down.
Check the connection you are actually using
A speed test on a phone in the same room is only a clue. The stick behind the television sees a worse signal. Move it onto 5 GHz Wi-Fi, or plug it into Ethernet. Pause cloud backups and console downloads on the same line. A match in the evening is when the rest of the house is online too.
HD needs about 10 Mbps held steady, not a peak that lasts one second. 4K needs about 25 Mbps with room to spare. If 4K pauses and HD does not, leave the player on FHD. The television will still look fine at a normal sofa distance.
One channel or every channel
If a single channel stalls and the next one plays, that stream is the problem. Tell support the channel name. If every channel stalls on Ethernet, then it is worth a message. Include the device model and a photo of any error, with the password covered.
Player settings are the last step
A slightly larger buffer can help on Wi-Fi after the signal is as good as you can make it. A huge buffer only delays the start. Hardware decoding should stay on unless one channel is a black screen. Do not install a second player “to fix the speed”. Two players do not make the Wi-Fi faster.
Our device guides list the buffer note for each box, because the menu is not in the same place on a Samsung TV as it is in TiviMate.