插畫・漫畫投稿&社群網站 - ART street by MediBang

I ask for small medibang lessons :)
Hi friends, thank you for your time! I would like to know from you why the word "undefined" appears in some illustrations. When I try to leave a heart or an emoticon the word undefined remains. In practice I cannot leave a reaction, can you tell me why?
I put below a screenshot
thanks (^ω^)

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