cannot access to mp3 file in node-red path

[RoboInk]

I can access to the mp3-file via internet browser: https://192.168.178.39/addons/red/doorbell
Using https://192.168.178.39/addons/red/doorbell as ms.url the speaker does not react.

However, the speaker does it's job with the esample provioded as: https://translate.google.com/translate_tts?ie=UTF-8&total=1&idx=0&textlen=32&client=tw-ob&q=Word%20Up&tl=En-gb

I do not see any difference. Can anybody help??