Websites we create are pwa they have manifest and sw, check blog.npub.pro
Discussion
Then it seems it sometimes (not always) fails to load one of the two files.
Browsers don't always suggest installing the app, it depends on what user did on the page etc. if you explicitly click add to homescreen does it suggest to install or tries to add shortcut?
Last time I tried with blog.npub.pro, it first only showed an add shortcut button, but later an installation prompt appeared. So I think it can take a while.