Thank you for your prompt response.
The first thing I checked when there was no Davx5 error was that the calendars are visible. All Calendars are set to visible in Google Calendar, but the entries for the Family Calendar are only displayed.!
I installed nextcloud 11.0.2 on a mutualized hosting ovh. The cloud works correctly. I have a problem with the synchronization between my android smartphone and the Web application.
I installed davdroid from f-droid and I configured the .htaccess with rerouting .well-known. I obtain my address books and my schedules but no synchronization. You can help me please.
503 Service not available seems to be a server problem. Did you ask Nextcloud support?
But synchronisation work between thunderbird (lightning) and (two direction) web application.
@TiCaillou Then it seems like the server error only appears in responses to DAVdroid requests. Did you ask Nextcloud support?
It working with caldav sync adapter but i have not addressbook.