Hello Lukasz,
The error indicates that you currently have a connector version that is no longer available for download configured in your product updates configuration in the Windows Policy associated with the selected group used to download the connector.
Please verify that this is not the case by editing the policy and checking the setting under Product updates. Even if it is blank please click the "Update Policy" button to update the policy and overwrite any previously configured product version. (The version may no longer be available which is why the field appears empty.)
Once this is done attempt to download the connector once again.
Let me know if you are successful.