Blazor Hybrid .apk application works with gRPC in Debug mode but gives error in Release mode

My Blazor Hybrid application has a login screen. When user enters his data and taps a button, the data is sent to the server via gRPC service.

When the application runs in Debug mode I see no errors and successfully sign in into my account.

But in Release mode I get the .apk file. I install it on my Android device and when try to login I get the error

Status(StatusCode="Unavailable", Detail="Error starting gRPC call.HttpRequestException: Permission denied (<domain-name:port>).SocketException: Permission denied",DebugException="System.Net.Http.HttpRequestException: Permission denied (<domain-name:port>)")

And I see no log in the terminal of the server, so I guess the request not even being sent.

1. What might cause such bizarre behaviour?

2. What is the difference between Release and Debug modes in Visual Studio?

UPDATE: It happens both on my physical Android device and Android emulator.