I started out by developing on Windows/Chrome and testing in Android/Chrome. My PWA also works in Mac/Chrome as far as I know. But I've been unable to load the Manifest file or Service Worker in IOS 11.2.5 on iPhone and iPad.
I enabled remote debugging on the iPad to find some errors but to no avail. However, I did notice that neither file was loaded under the Network tab.
I've gone on to discover that Manifest files might only be supported in IOS 13, according to caniuse and that also seems to be the same for Service Workers, can anyone confirm this?
tl;dr: Are Service Workers and Manifest files supported in IOS? and if so are they supported < IOS 11.3?
Service workers are not yet fully supported in iOS Devices. Your project will still work as per normal website but without the added benefits of the service workers. Until iOS 11.3 comes out to the public, we are still left clueless of what is and what is not supported in service workers.