Can't sync shared folder with user

Please help us by providing the following info. Before posting please make sure that you're running the latest available version for your oC release: https://owncloud.org/changelog/ + https://owncloud.org/changelog/desktop/

Steps to reproduce
1. create second user
2. share folder from main user with second user
3. webdav error when downloading files

Expected behaviour
sync

Actual behaviour
Exception: {"Message":"HTTP\/1.1 503 Encryption not ready: Private Key missing for user: please try to log-out and log-in again","Exception":"Sabre\DAV\Exception\ServiceUnavailable","Code":0,"Trace":"#0 \/var\/www\/owncloud\/3rdparty\/sabre\/dav\/lib\/DAV\/CorePlugin.php(83): OCA\DAV\Connector\Sabre\File->get()\n#1 [internal function]: Sabre\DAV\CorePlugin->httpGet(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))\n#2 \/var\/www\/owncloud\/3rdparty\/sabre\/event\/lib\/EventEmitterTrait.php(105): call_user_func_array(Array, Array)\n#3 \/var\/www\/owncloud\/3rdparty\/sabre\/dav\/lib\/DAV\/Server.php(459): Sabre\Event\EventEmitter->emit('method:GET', Array)\n#4 \/var\/www\/owncloud\/3rdparty\/sabre\/dav\/lib\/DAV\/Server.php(248): Sabre\DAV\Server->invokeMethod(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))\n#5 \/var\/www\/owncloud\/apps\/dav\/appinfo\/v1\/webdav.php(55): Sabre\DAV\Server->exec()\n#6 \/var\/www\/owncloud\/remote.php(138): require_once('\/var\/www\/ownclo...')\n#7 {main}","File":"\/var\/www\/owncloud\/apps\/dav\/lib\/connector\/sabre\/file.php","Line":311,"User":"wave"}

Client configuration
Client version: latest ubuntu client
Client operating system: ubuntu 16.04

Server configuration
Operating system: debian
Web server: 9.01
Database: sqllite
PHP version:
ownCloud version (see ownCloud admin page): 9.01
Updated from an older ownCloud or fresh install:
ownCloud log (data/owncloud.log):
Exception: {"Message":"HTTP\/1.1 503 Encryption not ready: Private Key missing for user: please try to log-out and log-in again","Exception":"Sabre\DAV\Exception\ServiceUnavailable","Code":0,"Trace":"#0 \/var\/www\/owncloud\/3rdparty\/sabre\/dav\/lib\/DAV\/CorePlugin.php(83): OCA\DAV\Connector\Sabre\File->get()\n#1 [internal function]: Sabre\DAV\CorePlugin->httpGet(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))\n#2 \/var\/www\/owncloud\/3rdparty\/sabre\/event\/lib\/EventEmitterTrait.php(105): call_user_func_array(Array, Array)\n#3 \/var\/www\/owncloud\/3rdparty\/sabre\/dav\/lib\/DAV\/Server.php(459): Sabre\Event\EventEmitter->emit('method:GET', Array)\n#4 \/var\/www\/owncloud\/3rdparty\/sabre\/dav\/lib\/DAV\/Server.php(248): Sabre\DAV\Server->invokeMethod(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))\n#5 \/var\/www\/owncloud\/apps\/dav\/appinfo\/v1\/webdav.php(55): Sabre\DAV\Server->exec()\n#6 \/var\/www\/owncloud\/remote.php(138): require_once('\/var\/www\/ownclo...')\n#7 {main}","File":"\/var\/www\/owncloud\/apps\/dav\/lib\/connector\/sabre\/file.php","Line":311,"User":"wave"}

Special configurations (external storage, external authentication, reverse proxy, server-side-encryption):
server side encryption

From the issue template shown when creating a new thread:

Before posting please make sure that you're running the latest available version for your oC release: https://owncloud.org/changelog/ + https://owncloud.org/changelog/desktop/

Before enabling encryption please also read AND understand:

Encryption keys are stored only on the ownCloud server, eliminating exposure of your data to third-party storage providers. The encryption app does not protect your data if your ownCloud server is compromised, and it does not prevent ownCloud administrators from reading user’s files. This would require client-side encryption, which this app does not provide. If your ownCloud server is not connected to any external storage services then it is better to use other encryption tools, such as file-level or whole-disk encryption.

After you're sure that you want to use the encryption app and after you have updated your installation to a recent oC version and the issue persists please create a new thread.