Webdav repository connection

Happy new year everybody !!

As the repository server is not working fast enough on wan due to local cache not present, I tried to setup a webdav repository. Unlucky as I am, I couldn’t make it work. I tried cli and gui but they both gave me the same error :

    $ kopia repository connect webdav --url=https://server.org/webdav/kopia
    Enter password to open repository: 
    kopia: error: unable to read format blob: ReadStream kopia.repository.f: 400, try --help

While I could connect successfully with cadaver :

    $ cadaver https://server.org/webdav/kopia
    Authentication required for kopia on server `server.org`:
    Username: myusername
    Password: 
    dav:/webdav/kopia/> put cleanfont.sh 
    Uploading cleanfont.sh to `/webdav/kopia/cleanfont.sh`:
    Progress: [=============================>] 100,0% of 1053 bytes succeeded.
    dav:/webdav/kopia/> 
    Connection to `server.org` closed.

Am I doing something wrong ?