Your ROOT_URL in app.ini is https://source.parasitstudio.de:63000/ but you are visiting https://source.parasitstudio.de/wirtz/OpenAudio_ArduinoLibrary/src/commit/ff049cad08088e7f2865d5953692367de6fe3892/examples/ReceiverPart2 You should set ROOT_URL correctly, otherwise the web may not work correctly.