MAVSDK-Python: timeout on command arm, takeoff etc.

I’m getting an error while using example 'takeoff_and_land.py":

Waiting for mavsdk_server to be ready...
Connected to mavsdk_server!
Waiting for drone to connect...
Drone discovered with UUID: 1
-- Arming
Traceback (most recent call last):
  File "test.py", line 37, in <module>
    loop.run_until_complete(run())
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python37\lib\asyncio\base_events.py", line 587, in run_until_complete
    return future.result()
  File "test.py", line 25, in run
    await drone.action.arm()
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python37\lib\site-packages\mavsdk\generated\action.py", line 230, in arm
    raise ActionError(result, "arm()")
mavsdk.generated.action.ActionError: TIMEOUT: 'Timeout'; origin: arm(); params: ()

What cause that problem? I’m connecting with pixhawk with esp8266 (pre build bin pixracer for connecting udp 14560 port) without any problems on mission planner app, but some kind of error appears using python example.