Why my login and register don't work when deployed (production) using .NET WebApi?

Question

In development the login and register work but in production it is not, why is that?

in account controller (API) I have the below code to login the user. I am using this example because it is shorter to demonstrate.

[HttpPost("login")]
    public async Task<IActionResult> Login(loginReqDto loginReq)
    {
        var user = await uow.UserRepository.Authenticate(loginReq.UserName, loginReq.Password);

        ApiError apiError = new ApiError();

        if(user == null)
        {
            apiError.ErrorCode = Unauthorized().StatusCode;
            apiError.ErrorMessage = "Invalid userId or Password!";
            apiError.ErrorDetails = "This is appearing when user or password does not exist!";
            return Unauthorized(apiError);
        }

        var loginRes = new LoginResDto();
        loginRes.UserName = user.Username;
        loginRes.Token = CreateJWT(user);
        return Ok(loginRes);
    }

and in my frontend (angular):

onlogin(loginForm: NgForm){

console.log(loginForm.value);
this.authServive.authUser(loginForm.value).subscribe(      
  (response: any) => {
    console.log(response);
    const user = response;
    localStorage.setItem('token', user.token);
    localStorage.setItem('userName', user.userName);
    this.alertify.success("You have loged-in successfully!");
    this.router.navigate(['/']);
  });
}

In Postman using development I am getting the code 200OK and generated the token. on the other hand, in production, I get internet server error code 500. Why?