There are two invalid icons in weather properties dialog in the "Move up" and "Move down" buttons. I took a screenshot. https://i.imgur.com/7WyxcnF.png
Maybe the theme you use doesn't provide them or your setup is faulty. With the (standard) awaita theme it shows two arrows here.
I have Adwaita as well version 3.34.0
What is the name of the icon files please so I can check if they are in the adwaita-icon-theme package?
Harald, is it possible you have gnome-icon-theme installed as well and Adwaita is set to inherit from it?
Hm. I have gnome-icon-theme-extras and -symbolic installed, both v3.12. I cannot answer the second question, I have not modified Adwaita but maybe my distribution does this. There is no gnome-icon-theme package in gentoo, it has been removed some time ago IIRC.
https://git.xfce.org/panel-plugins/xfce4-weather-plugin/tree/panel-plugin/weather-config.ui#n56 Icon names are 'up' and 'down'. The xfce4-panel preferences dialog uses 'go-up' and 'go-down' instead.
Andre Miranda referenced this bugreport in commit 9b10075594be707ff21ee09e4cdf8fc8aa8111d2 Use standard icon names (Bug #16059) https://git.xfce.org/panel-plugins/xfce4-weather-plugin/commit?id=9b10075594be707ff21ee09e4cdf8fc8aa8111d2
Hussam, can you please check if that commit fixes the problem for you? Thanks Theo for spotting this.
This is indeed fixed now. Thank you looking into this.