Today I've noticed that I no longer can sync my progress in Koreader. After clicking the sync progress buttun it freezes for 30 seconds and shows an error that sync failed and I should check my network connection. Is there some kind of sync server problem right now? I've check it on couple devices and different networks (WiFi and LTE) and the result is the same.
Edit:
I've found NiLuJe's comment on GitHub that the official sync server will be down for a few days.