Texteditor can't create a new file on external storage

[mattygazzo]

Hello, i'm using an owncloud installation on ubuntu 18.04 LTS and it works perfectly. I use an external smb/cifs storage with explicit username/password that can read/write on this folder. When i try to create a new txt file, a warning message appears "Could not create file "New text file.txt"". But when i try to create a txt on my user folder (not in an external storage) it works. Can you check please? Thank you