Plugin is invalid with Feeds Tamper

I am getting this message on the Feeds Tamper Page:
Error message
The specified plugin is invalid.

Steps to reproduce

I would like to import inline images from the node (Body fields) of a Drupal 7 site for a Drupal 9 site migration. This module looked promising but it is not working.

I am Using Drupal 9.5.8 with Feeds 8.x-3.0-beta3 and Feeds Tamper 8.x-2.0-beta3. I install the HTML Processors Module and choose "Href to Media" under the Body field in Tamper I get the error.

Any recommendations on how I can get this to work? Am I missing a step?