Missing agents

After adding some files to my PLEX library (server installed in a Synology NAS) I check that it does not look for the data.

When I go to search the data by hand so that the agents try to locate it I see that I do not have any.

I have no choice to select anything because there is nothing to show. I have restarted the server, the nas … but I do not have the solution.

That could be happening?

Thanks a lot!