Why vimspector does not stop at breakpoint in Python Flask

I'm trying to setup Flask debugging in NVIM.

When I debug a simple file and use break point (F9) vimspector works as charm.

a = 5
b = 10

def misko(a, b):
    c = 2
    a = c * a
    return a + b

if __name__ == "__main__":
    misko(a, b)

However, my usecase it to debug Flask app.

Vimspector simply does not stop at breakpoint.

{
  "configurations": {
    "env": {
      "ENV": "development",
      ...
    },
    "python: Launch at macbook": {
      "adapter": "debugpy",
      "configuration": {
        "name": "python: Launch",
        "type": "python",
        "request": "launch",
        "cwd": "${workspaceRoot}",
        "python": "${workspaceRoot}/venv-tmp/bin/python",
        "stopOnEntry": false,
        "console": "integratedTerminal",
        "program": "${workspaceRoot}/app.py"
      }
    }
  }
}