“Can’t connect to AWS!”

Hello,
I followed these instructions (https://aws.amazon.com/it/blogs/machine-learning/read-wordpress-sites-through-amazon-alexa-devices/) and created:
AWS access key
AWS secret key

However, when I insert them into the WP plugin, the following message appears:
“Can’t connect to AWS! Check your credentials and make sure your AWS accout is active!”

I repeated the procedure, regenerating the two keys, but I get the same error.

I tried it on two different sites.

What can it depend on?

Thanks