Custom symbols (only triangles) dont show on mobile

Hi, can you please help me? This is great plugin, but suddenly it stop showing custom symbols next to list on mobile. In pc its ok, in preview of template is ok. Only on mobile not. But its problem only if i put there little triangle. Tried copy of that from web, both versions of code… Tried to restart mobile, delete history of chrome in mobile. Nothing helped. Dont you know, what cause could do that? I didnt install some other plugins or something. Thanks a lot, guys:)

https://www.ads-software.com/plugins/collapsing-archives/