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/49e16b7876624efb638adaf8676e614225c7a454/examples/MixStereoToMono_Float
You should set ROOT_URL correctly, otherwise the web may not work correctly.