Could solve the problem. It was an issue from upgrading to MIUI 8.3. You have to do a full wipe of the phone.
Here the steps to solve the problem:
Backup the data with Option “Backup & Restore” in the MIUI-Settings (under Additional Settings)
Backup with TWRP
Backup all your data (Music, Pictures, Videos…) - they won’t be in the Xiaomi or TWRP Backup
Do a full wipe of system, data… in TWRP
Install the latest weekly build from xiaomi.eu
Restore from the Xiaomi-Backup
Install DavDroid - and it will work. It even fixed some other issues i had from the upgrades in MIUI
Of course it will be a bit work, but it’s worth anyway. So always make a Backup and a Restore from the Xiaomi-App from time to time…
Yes it is visible, on both S6 and S8.
I have got it to work, strangely by turning WiFi off and going via WAN.
On checking functionality, it is not syncing changes on made on phone (both S8 and S6) back to Server side, LAN or WAN, but it is syncing changes made on server. So I will look into this a bit more. As this is on both phones, I’m assuming its probably a permission thing. Will update forum when I have resolved issue or not!