Polly: Warning. The service encountered a problem. Try again

Based on the error message you're receiving when trying to use Amazon Polly, there could be a few potential causes:

1. IAM Permissions Issue: You might not have the correct permissions to access the Amazon Polly service. If you're using an IAM user account, your administrator needs to ensure you have the appropriate permissions. This could be done by attaching the "AmazonPollyFullAccess" policy to your user or by creating a custom policy that grants specific Polly permissions.

2. Service Availability: There might be a temporary issue with the Amazon Polly service in your region. In this case, waiting and trying again later might resolve the problem.

3. Input Text Format: If you're using SSML tags in your input text, make sure they're properly formatted. Special characters like "<", ">", and "'" need to be escaped in SSML to avoid "Invalid SSML request" errors.

4. Browser Issues: Try clearing your browser cache or using a different browser to access the Polly console.

If the issue persists, you might want to check the AWS Service Health Dashboard to see if there are any known issues with Polly, or contact AWS Support for further assistance.
Sources
Accessing AWS Service Polly as IAM user | AWS re:Post
How to use Amazon Polly to resolve common implementation challenges | AWS re:Post