Getting Failed to execute 'addAll' on 'Cache': Request failed error

[vincentwansink]

Error in Chrome Console

Uncaught (in promise) TypeError: Failed to execute 'addAll' on 'Cache': Request failed
Promise.then (async)
(anonymous) @ upup.sw.min.js:6
Promise.then (async)
_parseSettingsAndCache @ upup.sw.min.js:6
(anonymous) @ upup.sw.min.js:6

Steps to Reproduce (for bugs)

Currently this is all I have:

<script src="/upup.min.js"></script>
<script>

  //<!--****************************************************************************-->
  //<!--*** Register service worker for offline use
  //<!--****************************************************************************-->

  UpUp.start({
    'content-url': 'offline.htm',
    'assets': [
    ]  
  });
</script>

I removed the assets just to make sure one of my assets wasn't causing the problem, but regardless I had previously confirmed that they all exist. And yes, offline.htm also exists. I have added the following files to the root of my website

• upup.min.js
• upup.min.js.map
• upup.sw.min.js
• upup.sw.min.js.map

Lighthouse gives me an all green score for PWA requirements, yet I'm still getting this error both in Chrome and Edge. Edge is actually worse because it seems to be stuck in a perpetual "Offline" state, even though it's clearly online, and it's failing to load a couple of my icons and my common.js file though I suspect if I can get upup to play nice with Chrome, Edge will follow suit.

Are there other upup files I need to upload to my server? I can't find any reference to this in the documentation.