Error on banner install

I'm using this page: https://developers.google.com/web/fundamentals/engage-and-retain/app-install-banners/ to create a web app banner install.

I have the sw.js as service worker in public/admin/
I have registered with success the service worker
and i have the manifest.json in public/admin too like this
```

{
"name": "Web App Install",
"short_name": "Admin",
"icons": [
{
"src": "/admin/mstile-70x70.png",
"sizes": "36x36",
"type": "image/png"
},
{
"src": "/admin/mstile-70x70.png",
"sizes": "48x48",
"type": "image/png"
},
{
"src": "/admin/mstile-70x70.png",
"sizes": "72x72",
"type": "image/png"
},
{
"src": "/admin/mstile-70x70.png",
"sizes": "96x96",
"type": "image/png"
},
{
"src": "/admin/mstile-70x70.png",
"sizes": "144x144",
"type": "image/png"
},
{
"src": "/admin/mstile-70x70.png",
"sizes": "192x192",
"type": "image/png"
}
],
"start_url": ".",
"display": "standalone",
"related_applications": [{
"platform": "web"
}],
"related_applications": [],
"prefer_related_applications": false
}
```
in dev tools

the link of service worker is: https://01f1c2fb.ngrok/admin/pt

the link of manifest.json is https://01f1c2fb.ngrok/admin/manifest.json

but i'm getting an error on trying install the web app
the error is

"Site cannot be installed: no matching service worker detected. You may need to reload the page, or check that the service worker for the current page also controls the start URL from the manifest"

Can someone help me please.
Thanks in advance.
Carlos Vieira