Synchronization of the local folder on the remote server to the client

Hello everyone, I have a synchronization problem.

when I add a file via a nextcloud client (desktop, smartphone), I find this file on my NAS.

But the opposite doesn’t happen. if I add a file on my NAS server directly. There is no synchronization done and I can’t find this file on my clients.

do you have a solution please?

How do you have the NAS connected to Nextcloud?

my nextcloud server is directly on my nas.