Unable to retrieve URL needed for download

Server Version#: 1.14.1.5488

Hi,
i’m trying to upgrade PMS to the latest version.
Using the upgradePlex command on Ubuntu it returns the message :
Authenticating … OK
Finding download URL to download … OK
ERROR: Unable to retrieve the URL needed for download (Query DISTRO: ubuntu, BUILD: linux-ubuntu-x86_64)

Do someone has an idea ?
Many thanks.
Corentin