Keycloak token not fetched

[ArzelaAscoIi]

Hi,
I am facing some problems with openid-connect and keycloak. I am using Keycloak as user management for our website.
I registered a client (see screenshot and replace the <...> values)

and added the following configuration at @nuxtjs/auth-next

auth: {
    strategies: {
      keycloak: {
        scheme: 'oauth2',
        endpoints: {
          authorization: 'https://<server.com>/auth/realms/<realm>/protocol/openid-connect/auth',
          userInfo: 'https://<server.com>/auth/realms/<realm>/protocol/openid-connect/userinfo',
          token: 'https://<server.com>/auth/realms/<realm>/protocol/openid-connect/token',
          logout: 'https://<server.com>/auth/realms/<realm>/protocol/openid-connect/logout?redirect_uri=<mydomain.com>/login'
        },
        token: {
          property: 'access_token',
          type: 'Bearer',
          name: 'Authorization',
          maxAge: 1800
        },
        refreshToken: {
          property: 'refresh_token',
          maxAge: 60 * 60 * 24 * 30
        },
        //responseType: 'token',  // implicit flow works thoug, but i want to use refresh tokens
        //grantType: 'implicit',
        responseType: 'code',  
        grantType: 'authorization_code',
        clientId: '<client>',
        scope: ['email', 'roles', 'address'],
        codeChallengeMethod: 'S256'
      }
    },
    plugins: ['~/plugins/auth'],
    redirect: {
      login: '/login',
      logout: '/',
      callback: '/callback',
      home: '/'
    }
}

This works if I run the development server. If I publish the page using AWS Amplify (static) the authentication breaks...
I am redirected to the local page /callback (I use the example callback.vue from the demo), but no tokens are set.
The local storage contains the following values:
auth.keycloak.pkce_code_verifier: "a7ad2a766..."
auth.keycloak.pkce_state: "b895b04..."
auth.redirect: "/"
auth.strategy: "keycloak"

There are no logs inside the console.

Can somebody help me out here ? I am struggeling now for >3 days...

[ArzelaAscoIi]

If I run the development server I get a 200 response from "callback?state=...". After deploying it (ssr:false) this returnes a 301.