When going offline, I get the following error by my service worker:
(unknown) #3016 An unknown error occurred when fetching the script
my service w
Before trying anything else, check whether your https certificate is invalid or not matching the url you are accessing.
E.g. In my case I was trying to access https://localhost with a certificate that was registered for another domain.
While hitting "proceed" would allow me to enter to the site, this exact error would be printed to the console:
An unknown error occurred when fetching the script