Problem with scanner

I notice that when I use a button to navigate to a separate screen (I’ve tried using bottom bar navigator wit the same results), and use this code:
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The scanner wont be brought up, I think it’s a bug because before this it could work. Any help?

try it easier - run through the button! this should work. Perhaps you don’t have permission to use your camera?
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thats because Open and start block is not working properly