unable to access amazon comprehend and other services

Based on your description, you're experiencing an access issue with Amazon Comprehend after starting a free trial. This could be related to IAM permissions rather than an issue with your account verification.

Even when using the free tier, you need to have the proper IAM permissions configured to access Amazon Comprehend. The error message suggesting you need a "paid subscription" or to "complete verification" might indicate that your IAM user doesn't have the necessary permissions to perform Comprehend operations.

To resolve this issue:

1. Check whether your IAM user has the appropriate permissions for Amazon Comprehend operations. You may need to attach a policy to your IAM user that allows Comprehend actions.

2. If you're using the root account, ensure that your account activation is fully complete. Sometimes there can be delays between account verification and full service activation.

3. Verify that you're in a supported AWS Region for Amazon Comprehend, as not all services are available in all regions.

4. If you recently created your account, it might take up to 24 hours for all services to become fully accessible.

If you continue to experience issues after checking these items, you might want to contact AWS Support for further assistance with your specific account situation.
Sources
Troubleshooting Amazon Comprehend identity and access - Amazon Comprehend
Access to Textract on Free Version | AWS re:Post