Get an error in nbviewer jupyter

[calpe]

Hello,

I have a notebook in my bitbucket repository with the following url: https://bitbucket.org/calpe/notebooks/raw/tip/july17_phd_meeting.ipynb

I would like to open it with a jupyter nbviewer with the url: http://nbviewer.jupyter.org/urls/bitbucket.org/calpe/notebooks/raw/tip/july17_phd_meeting.ipynb

Always I get an error saying:
400: Bad request
We couldn't render your notebook
Perhaps it is not valid JSON, or not the right URL.
If this should be a working notebook, please let us know.
The error was: Error reading JSON notebook

Do you have an idea what can cause that?

Thanks!