Server currently not available on Samsung TV

[tom80H]

Is that by any chance an older Samsung model with a Tizen version older than version 2.4 or a Smart Hub model?
If so you might want to check out this recent announcement

Important information about Plex for smart TVs after September 30, 2021

UPDATE: It appears that all Tizen-based Samsung sets are likely affected by the cert change and will thus need the app and server configured to allow insecure connections. On September 30, 2021, some older smart TVs (some Samsung, LG, Vizio, Hisense, and other unsupported TV platforms) will no longer be able to use secure connections to communicate with Plex Media Servers. These devices are no longer supported by their manufacturers, and won’t be receiving an update needed to continue making se…