Cannot Write/Delete into mounted Local External Storage

Hi, I am running Nextcloud using (Ubuntu+Docker) and manage to mount my TrueNAS to Ubuntu host. - Mounted to /mnt/

So I want to share this directory to Nextcloud and already mounted it using Local External Storage → /mnt/ : /mnt/truenas and give name “nas”
Shared dataset from truenas → Games and Software

Success read in Nextcloud web and mobile app. But cannot create new folder/file/upload to the “nas” directory. Thought that something wrong with my TrueNAS and try to mount host directory /opt and /www as Local External Storage but also get “Operation is blocked by access control”.

Can write normally to default Nextcloud folder like Photo and Documents.

Thanks in advance.