Post not being converted to speech due to undefined variable.

[jorgecodster]

Steps:

1. Create a Wordpress post.
2. In the Amazon Polly tab below the post, check that Text-To-Speech (Amazon Polly) is on.
3. Select the language and click on the Translate button to start processing.

Visual hint of error: Progress bar appears and animation starts but it never ends.

The console shows the following message:
Uncaught ReferenceError: pollyajax is not defined
at amazonPollyTransProcessStep (amazonpolly-admin.js:69)
at HTMLButtonElement. (amazonpolly-admin.js:142)
at HTMLButtonElement.dispatch (load-scripts.php?c=0&load[chunk_0]=jquery,utils&ver=5.5:3)
at HTMLButtonElement.r.handle (load-scripts.php?c=0&load[chunk_0]=jquery,utils&ver=5.5:3)

Technical details:
Wordpress: 5.5
AWS for Wordpress: 4.2.2
Language to process: Spanish - Mia
Other plugins: Hubspot (7.40.0), Elementor (2.9.14)