• KOReader version: up to 06bd4d7
• Device: independent, but I have tried on Kobo, Kindle voyage and Android

Issue

Devices cannot connect to default sync server. Unknown error reported.

Steps to reproduce

If it's expected, I happen to setup a sync server at hzj-jie-ubuntu.westus.cloudapp.azure.com:7200. Feel free to try it and update the default setting.