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/ae99656d297540dbd8abde5cd2ac3eba5449b09b/examples/MixStereoToMono_Float You should set ROOT_URL correctly, otherwise the web may not work correctly.