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/03c774f77f201eaad1975bc7471c52ed99206d1d/examples/MixStereoToMono_Float You should set ROOT_URL correctly, otherwise the web may not work correctly.