Cifs share access problem


I am encountering a problem with external_storage application.
I am trying to give access to a netapp cifs server but it does not work.
php-smbclient is installed and working on it. ( smbclient command line, mount -t cifs, too)
But not nextcloud 13, neither 14.
The OS is Ubuntu 18.04.
All I can say is that, cifs works on nextcloud with other Windows servers.
The difference between them is that on the netapp that fails no information about the size is given, contrary to the others and when trying to access the cifs share the message returned is :
“error with the server: empty response given …”

If anyone can help.