Address book with name 'contacts' could not be found

Hello,
I recently started using NextCloud 11 (hosted by Framasoft) + CardBook to sync my 3 address books on Thunderbird.
First 2 went fine but for some reason, the 3rd one won’t sync.
Account created on NextCloud.
When trying to sync CardBook fails to validate the account. The given reason in the log file is Address book with name ‘contacts’ could not be found.
I tried creating a new adress book within the same NextCloud account, same thing.
I event created a new fresh NextCloud account, same issue.
The detailed log is the following:

2017.07.18 22:28:40:229 : Validation module : Validating without discovery request on https://framagenda.org/remote.php/dav/addressbooks/users/demospheretoulouse/contacts/ …
2017.07.18 22:28:40:245 : Validation module : debug mode : method : (new String("PROPFIND"))
2017.07.18 22:28:40:245 : Validation module : debug mode : body : (new String("<?xml version=\"1.0\" encoding=\"utf-8\"?><D:propfind xmlns:D=\"DAV:\"><D:prop><D:resourcetype/><D:displayname/></D:prop></D:propfind>"))
2017.07.18 22:28:40:245 : Validation module : debug mode : headers : (new String("({depth:\"1\", 'content-type':\"application/xml; charset=utf-8\", 'User-Agent':\"Thunderbird CardBook/20.7\", Authorization:\"Basic ZGVtb3NwaGVyZXRvdWxvdXNlOlRzYWNhbWFpbjEwMA==\"})"))
2017.07.18 22:28:40:245 : Validation module : debug mode : username : (new String("demospheretoulouse"))
2017.07.18 22:28:40:246 : Validation module : debug mode : url : (new String("https://framagenda.org/remote.php/dav/addressbooks/users/demospheretoulouse/contacts/"))
2017.07.18 22:28:40:454 : Validation module : debug mode : response text : (new String("<?xml version=\"1.0\" encoding=\"utf-8\"?>\n<d:error xmlns:d=\"DAV:\" xmlns:s=\"http://sabredav.org/ns\">\n  <s:exception>Sabre\\DAV\\Exception\\NotFound</s:exception>\n  <s:message>Addressbook with name 'contacts' could not be found</s:message>\n</d:error>\n"))
2017.07.18 22:28:40:454 : Validation module : debug mode : response code : (new Number(404))
2017.07.18 22:28:40:456 : Validation module : Synchronization failed (step : validateWithoutDiscovery, url : https://framagenda.org/remote.php/dav/addressbooks/users/demospheretoulouse/contacts/, status : 404)
2017.07.18 22:28:41:247 : Validation module : debug mode : cardbookRepository.cardbookServerDiscoveryRequest : (new Number(1))
2017.07.18 22:28:41:248 : Validation module : debug mode : cardbookRepository.cardbookServerDiscoveryResponse : (new Number(1))
2017.07.18 22:28:41:249 : Validation module : debug mode : cardbookRepository.cardbookServerDiscoveryError : (new Number(1))
2017.07.18 22:28:41:249 : Validation module : debug mode : cardbookRepository.cardbookServerValidation : ({'https://framagenda.org':[]})

Any idea what could be wrong here?
Thanks in advance for your help.

P.