Saw this message on the Details tab:
"Met.no sunrise API states that this version of the webservice
is deprecated, and the plugin needs to be adapted to use
a newer version, or it will stop working within a few months.
Please file a bug on https://bugzilla.xfce.org if no one
else has done so yet."

Xubuntu 18.04.2 --  xfce4-weather-plugin 0.8.10
latest version from https://launchpad.net/xfce4-weather-plugin