No link to add comment

I can't get react_comments 8.x-1.0-beta2 to work with Drupal 8.9.1 on MAMP (PHP 7.3.9)

The comments are loaded by JS (I get the blue spinning circle) and the layout has changed, so something is happening. The heading line appears with names and permalink. But there is no link to reply to comments, and the link to comment directly on the node takes me to the standard comment page.

Changing theme (Bartik) seems not to make any difference.

I have a couple of failed to load resource errors in the console:

[Error] Failed to load resource: the server responded with a status of 404 (Not Found) http://localhost:8888/modules/react_comments/css/dist/main.229d614e.css.map

[Error] Failed to load resource: the server responded with a status of 404 (Not Found) http://localhost:8888/modules/react_comments/js/dist/main.29c5c118.js.map

I am also getting two
tags inserted between paragraphs in the comments.