The problem

I received the following error when attempting to use the installPlugin function.

Uncaught (in promise) TypeError: Failed to construct 'FormData': parameter 1 is not of type 'HTMLFormElement'.

Some troubleshooting

The error originated from line 16:

I checked the selectors, and they look right. Perhaps it is something wrong with the request in the following? I double checked the url and it works in a regular WordPress instance. But I am unfamiliar with how to debug a request through the ServiceWorker.

Additional information

This is the project in which I am getting the error. It's pretty simple, I'm just trying to figure out a bare minimum implementation of this to showcase a plugin in development.

https://github.com/johnhooks/playground-experiment

The current version of the site is hosted here if you want to examine the issue in the wild.

https://johnhooks.io/playground-experiment/