I guess this is the problem :
Exception: {"Message":"HTTP\/1.1 403 Unsupported client version.","Code":0,"Trace":"#0 [internal function]: OC\\Connector\\Sabre\\BlockLegacyClientPlugin->beforeHandler(Object(Sabre\\HTTP\\Request), Object(Sabre\\HTTP\\Response))\n#1 \/var\/www\/owncloud\/3rdparty\/sabre\/event\/lib\/EventEmitterTrait.php(105): call_user_func_array(Array, Array)\n#2 \/var\/www\/owncloud\/3rdparty\/sabre\/dav\/lib\/DAV\/Server.php(456): Sabre\\Event\\EventEmitter->emit('beforeMethod', Array)\n#3 \/var\/www\/owncloud\/3rdparty\/sabre\/dav\/lib\/DAV\/Server.php(254): Sabre\\DAV\\Server->invokeMethod(Object(Sabre\\HTTP\\Request), Object(Sabre\\HTTP\\Response))\n#4 \/var\/www\/owncloud\/apps\/files\/appinfo\/remote.php(83): Sabre\\DAV\\Server->exec()\n#5 \/var\/www\/owncloud\/remote.php(132): require_once('\/var\/www\/ownclo...')\n#6 {main}","File":"\/var\/www\/owncloud\/lib\/private\/connector\/sabre\/blocklegacyclientplugin.php","Line":76}
But how to solve it is another question.