JS error when synchronising external calendar

I have a problem with the calendar. I would like to add a calendar with the french public holidays, so I tried to add this iCals :

Unfortunatly, it doesn’t work. For the Google one, I get a HTTP 401 error (and the calendar isn’t added). For the webcal one, the calendar is added but not displayed because of a JS error :

Failed to load resource: the server responded with a status of 500 (Internal Server Error) 

How can I add an external calendar? Tell me if you need more details (I’m new with NextCloud).

Dark Patate.