What server version are you running? If you are still on 10.9 or 10.10.4 and older, that would be why. The plugin currently only supports 10.10.5 and newer.
Jellyfin 10.10.6 (Docker)
Ubuntu 24.04.2 LTS w/HWE
Intel i3 12100
Intel Arc A380
OS drive - SK Hynix P41 1TB
Storage
4x WD Red Pro 6TB CMR in RAIDZ1
If it is just plain docker, you would just "pull" the latest image. Assuming the container is set to the "latest" tag. If the container is set to a specific version tag, you would need to manually change the version number.
Jellyfin 10.10.6 (Docker)
Ubuntu 24.04.2 LTS w/HWE
Intel i3 12100
Intel Arc A380
OS drive - SK Hynix P41 1TB
Storage
4x WD Red Pro 6TB CMR in RAIDZ1