I dived into this subject and discovered that I had to assign the rights of the group that contained the translation service, separately to Polly too.
Logical of course, but one has to know ...
Granted rights and now Polly doesn't stop talking. How to shut her off?
It works here. The TTS service has been tested on Macs with both Apple and Intel chips. Perhaps you need to create new keys in Identity and Access Management (IAM) Dashboard at your Amazon (AWS) account.
Sorry, but I cannot get it to work...
No voice to select, no nothing.