I am testing a new WP site, pure AMP. I am using this AMP plugin: https://github.com/ampproject/amp-wp/graphs/contributors

Sitewide, I have no other errors whatsoever.

AMP does not allow the use of JS <script> tags unless they are for loading AMP components, which are added automatically by the AMP plugin. For any page to be served as AMP, all invalid script tags must be removed from the page. Instead of custom or third-party JS, please consider using AMP components and functionality such as amp-bind and actions and events (as opposed to JS event handler attributes like onclick). Some custom JS can be added if encapsulated in the amp-script. Learn more about how AMP works.

If all invalid markup is “removed” the page will be served as AMP. However, the impact that the removal has on the page must be assessed to determine if the result is acceptable. If any invalid markup is “kept” then the page will not be served as AMP.
Error code
DISALLOWED_TAG
Invalid markup
<script … >
Element attributes
type text/javascript
src https://mysite.net/pwa-register-sw.js
id pwa-main-script-js
Element name
script
Parent element
body
Sources