Hi,
you wrote that the host is already existing. Did you allow the fileconnector to overtake the host?
You can check by opening the host details and go to the bottom. At my test site it looks like this:
Important is that the locked by field references your site and the name of your dcd connection. If it does not mention this you will have to allow the fileconnector to take over hosts by editing your connection and then activate Take over existing hosts.
After that please save and re-run the connection.
If this does not help I’d suggest increasing the DCD log level (in WATO go to Setup → Dynamic configuration logging and set general messages to Debug) and then having a look at the log of your connection.
If you see a message like Host 'data19' already exists as an unrelated host it is an indicator that the host is currently not managed by the plugin and it will not attempt to alter it.
Please let me know if this helps you!
Cheers
Niko