Please register at https://mobsted.com/better_pwa_widgets
This service is well explained within the service itself. Th only question we get, which is also explained inside - "My Service Worker checks out as Yellow, not green. Will this work?" The answer is - it is often impossible to 100% make sure that Workers are ok using outside analytics, like ours. SO, if you see that standard App Saving Prompts do function well, then do not pay attention to the Yellow light here as well.
So the only 100% requirement for Mobsted Custom Prompts to work - YOU MUST HAVE A WORKING PWA ON YOUR WEBSITE ALREADY.