Check the following two points.

1. The cause may be that the access to the domain “api.stock-app.jp” is blocked.

Change the network and security settings to permit the access to “*.stock-app.jp”, since you need to permit the accesses to all the subdomains of “stock-app.jp”.

2. Stock uses not only “https: (port443)” protocol but also “wss:(port443)”.

Permit both protocols if you block accesses with protocol.