Hi, @Franco!
Thank you for using matterpoll-emoji. I’m developer of matteropll-emoji.
I encountered the same issue at few month ago, and it had been solved.
We have released matterpoll-emoji v0.1.1 that includes fixes for this problem.
If you’re using Mattermost v4.2.2 or above, I think that you have to use matterpoll-emoji v0.1.1 or above.