Why do citation links in Google Docs lead to an error page?

Our extension uses URLs to encode citation information in Google Docs. This error page appears because citation links are internal and not meant to lead anywhere.

If clicking an in-text citation shows this...

... please reload the document and restart the extension via the Chrome menu  > More Tools > Extensions, switching Paperpile off/on. You can also restart Chrome, which restarts all extensions.

The correct citation dialog should look like this...

... then clicking the pencil icon > blue bubble will open advanced citation options, including Open in Paperpile: