Node.js + Angular : Cors problem – fly.toml

I would need help with my deployment issue on “fly.io” platform. Communication between the frontend and backend is functional for a while, but then this error occurs:

“Acess to XMLHttpRequest at ‘https://todo-backend.fly.dev’ from origin ‘https://todo-frontend.fly.dev’ has been blocked by CORS policy: No ‘Access-Control-Allow-Origin’ header is present on the requested resource.”

where the problem is that I am not sending the header from the frontend to the backend, which was previously being sent and suddenly stopped. My application works fine until I transferred it to this platform. May I ask how someone else solved this issue?
My backend configuration is as follows:

app.use(
  cors({
    origin: [
      "https://todo-front.fly.dev",
    ],
    credentials: true,
  })
);

backend log:
enter image description here

And this is my frontend configuration:

httpOptions = {
    headers: new HttpHeaders({
      'Content-Type': 'application/json',
      'Access-Control-Allow-Origin': 'https://todo-frontend.fly.dev',
    }),
    responseType: 'text' as 'json',
    withCredentials: true,
  };

fly.toml frontend:

app = "todo-front"
kill_signal = "SIGINT"
kill_timeout = 5
processes = []

[env]

[experimental]
  allowed_public_ports = []
  auto_rollback = true

[[services]]
  http_checks = []
  internal_port = 8080
  processes = ["app"]
  protocol = "tcp"
  script_checks = []
  [services.concurrency]
    hard_limit = 25
    soft_limit = 20
    type = "connections"

  [[services.ports]]
    force_https = true
    handlers = ["http"]
    port = 80

  [[services.ports]]
    handlers = ["tls", "http"]
    port = 443

  [[services.tcp_checks]]
    grace_period = "1s"
    interval = "15s"
    restart_limit = 0
    timeout = "2s"

fly.toml backend:

app = "todo-back"
kill_signal = "SIGINT"
kill_timeout = 5
processes = []

[env]
  ALLOWED_ORIGINS = "https://todo-frontend.fly.dev"
[experimental]
  allowed_public_ports = []
  auto_rollback = true

[[services]]
  http_checks = []
  internal_port = 3000
  processes = ["app"]
  protocol = "tcp"
  script_checks = []
  [services.concurrency]
    hard_limit = 25
    soft_limit = 20
    type = "connections"

  [[services.ports]]
    force_https = true
    handlers = ["http"]
    port = 80

  [[services.ports]]
    handlers = ["tls", "http"]
    port = 443

  [[services.tcp_checks]]
    grace_period = "1s"
    interval = "15s"
    restart_limit = 0
    timeout = "2s"

Thank you in advance

I have tried to change ‘Access-Control-Allow-Origin’: ‘https://todo-frontend.fly.dev’ to
‘Access-Control-Allow-Origin’: ‘*’ etc. nothing works. Is it problem of the hosting?