Amazon prime app says "Something went wrong. Please try again later. For more help, visit amazon.co.uk/videohelp." whenever I use Amazon on either of our BT boxes. Amazon works fine on my tablet and phone, so definitely BT box issue. It said this a few times, worked once, now says this message again everytime...
Did you read the customer reviews before installing the Alexa skill, it doesn't have a good rating.
I Could be wrong but I read it that the OP is using the Amazon Prime app on the BT Box, not using any skills or his voice