CSS not loading on a widget.

hi, 

i have a problem with a widget plugins that i'ive made, it's a weather widget working with the dark sky API, i have to use my own icons, so i used the weather icons from https://erikflowers.github.io/weather-icons/ i've tried everything in the code, and the only thing showing on the widget is a little square instead of the wanted icons.

Can someone help me ? Thanks,

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