When accessing Immich through the domain behind Nginx, the application logs into a different user session than when accessing via the local IP. Since Immich stores photos with per-user ownership, the domain session ends up trying to access assets that belong to another account.
As a result:
The photo thumbnails are visible
But when a photo is opened, Immich returns the error:
Edit: I have tried both cloudflare tunnel and nginx reverse proxy. Same issue