Are you able to paste a screenshot of the entire Trello window with the sidebar open (the one you posted above where it says  Add Power-Up...) at the time you try to add the powerup? I'm trying to see the error that you see but its not showing in the screenshots you posted?
Hello Community! My name is Brittany Joiner and I am a Trello enthusiast and Atlassian Community Leader. I'll be sharing with you a series of videos with my top tips on how to best use Trello...
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