Camara to FTP connection

MyCloudEX2Ultra 3TB.
Firmware 2.31.204
Username (camuser) and appropriate password (tried admin user and both shares!)
Public share with FTP ON and its defaults and no IPs blocked
Extended Logging set ON

I have two cameras which have the same setup pointing to with the appropriate folder path on the Public share and they connect to MyCloud with no problem.

I have a third camera on my network where FTP is set to the correct IP, username and password and will refuses to connect to MyCloud.

However, I can connect this camera to my PC where IIS FTP site points to a folder on my PC with no problem.

FTP Access is ON and also ON for the share (Anonymous None - tried the other options).
Tried setting MyCloud with AFP access, NFS access and WebDAV Service all ON
Tried various combinations of these settings, but to no avail.
Tried different FTP configurations including each of the Client Languages, Implicit and Explicit TLS, FXP On and OFF

The log shows the camera Logging On and then Logging Off. Nothing reported as happening in between. The other cameras log on, do something and then log of.

Tried the camera with folder path and without folder path (format: fName/fName/fName with forward and back slashes). Tried the same configurations for both shares.

Has any one got a sensible suggestion (apart from throwing the camera away, which is rapidly becoming a good option).

PS The cameras all use Passive Mode!!!