The Subtitle Extract plugin runs on a schedule. You can go to the dashboard and run it manually. Depending on how big your library is it might take some time.
Jellyfin 10.10.3 (Docker)
Ubuntu 24.04 LTS
Intel i3 12100
Intel Arc A380
OS drive - SK Hynix P41 1TB
Storage
3x WD Red Pro 6TB CMR in RAIDZ1 (JF Library)