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/72390e9dc7e4463514a1c2d43920d2a28a51d4bb/examples/MixStereoToMono_Float You should set ROOT_URL correctly, otherwise the web may not work correctly.