So what is your setup now? Where does everything run? On the synology (official or synocommunity packages) or in docker?
If you have sonarr in docker, this obviously won’t work because those paths are not available inside the docker container:
Not sure if there are people who use synoindex in combination with sonarr in docker, but my first idea would be to map the folders in the command above to volumes in the container with exactly the same name.
If you run sonarr as a native package (synocommunity), forget all of the above.
Crank logging up to trace and hopefully a reply with an error that will show what’s wrong is coming from the synoindex command.
As an alternative or if synoindex doesn’t reply to sonarr and you see nothing in trace logs:
I may be wrong, but I vaguely remember synoindex creating its own logs? Try to locate those and see if it reports any issues why the file is not indexed.
Second issue seems to be permissions? (Post before last one with the 777 bandaid) It’s clear that not everything runs as a user in the same group, or for simplicity just run everything as the same user. The last option is less secure but imo for a home system doesn’t matter as long as you don’t pick root or a typical overprivileged “administrator” user you make in the synology gui.
Or, if that’s working now, just don’t touch it anymore