Gnosis Safe – How to Solve: ‘Failed to Fetch App Manifest’ Error When Adding App to Gnosis Safe

I have created React app and trying to connect users ethereum account via gnosis-safe. I'm added manifest.json content as required here https://docs.gnosis-safe.io/build/sdks/safe-apps/releasing-your-safe-app but still got an error Failed to fetch app manifest while trying add my app in safe app.

To connect safe wallet I'm using react-web3 and @gnosis.pm/safe-apps-web3-react connector.

I'm 100% sure that manifest.json and logo available in the app root by url.

here my manifest.json

  {"short_name": "Appname",
  "name": "Appname",
  "description": "A platform for ...",
  "iconPath": "./logo.svg",
  "icons": [
    {
      "src": "favicon.ico",
      "sizes": "64x64 32x32 24x24 16x16",
      "type": "image/x-icon"
    },
    {
      "src": "logo192.png",
      "type": "image/png",
      "sizes": "192x192"
    },
    {
      "src": "logo512.png",
      "type": "image/png",
      "sizes": "512x512"
    }
  ],
  "start_url": ".",
  "display": "standalone",
  "theme_color": "#000000",
  "background_color": "#ffffff"
}

I need only get user's ethereum address, not sending any transactions, so I don't think I need add some Sdk's etc. Can anybody help me? Maybe there is a simple way to validate my manifest or check how it fetching from my app?