push device config to phone fails (Executed failed,Can't connect to server)

[haroem]

in-band provisioning enabled in skype4b 2015 on-prem.
just trying to use YDMP to centrally manage device config in a one to many publish scenario.
pushing test messages works fine, remote reboots are fine.
phones themselves work fine.

any chance to get a better idea of why config won't push to phones?

Thanks.