Unable to synchronise contacts with iphone

i followed (or i have the impression i followed) all the instructions of the manual page :

  1. Open the settings application.
  2. Select Mail, Contacts, Calendars.
  3. Select Add Account.
  4. Select Other as account type.
  5. Select Add CardDAV account.
  6. For server, type example.com/remote.php/dav/principals/users/USERNAME/ 7. Enter your user name and password.
  7. Select Next.
  8. If your server does not support SSL, a warning will be displayed. Select Continue.
  9. If the iPhone is unable to verify the account information perform the following: • Select OK.
    • Select advanced settings.
    • If your server does not support SSL, make sure Use SSL is set to OFF. • Change port to 80.
    • Go back to account information and hit Save.
    Now should now find your contacts in the address book of your iPhone. If it’s still not working, have a look at the Troubleshooting and Troubleshooting Contacts & Calendar guides.

but it didn’t work : unable to synchronize

do you have any idea what i could do ?

Especially on iOS I made good experience with service discovery:

It also helps to check your server logfiles, this way you see what the client is looking for (like the service discovery urls, and if it can’t find it, what it is doing next).

hello i had an error with the url of the servor ; as indicated in my former post, this adress is obtained by just clicking on “copy the link” on the web interface’s display of the contacts

now it remains a question for me :
i created new contacts on my mac, on nextcloud’s web interface, on my iphone
the synchronisation between this tree “places” is perfect except for the iphone :
new contacts created on the my or on nexcloud are displayed on the iphone
but :
new contact created from ios does not appear neither on my mac carddav client (i.e. the apple application named “contacts” and integrated in mac os X) nor on my nextcloud’s contact page on the web
thought, if i modify a contact from ios, the modification appears on the mac
do you think i’ve made something wrong ?