Thank you a lot. I'm not sure what extracly message was at the first time, but now it's "Cannot identify destination folder" as you said. And as stated in the article you noticed .sync subdirectory is empty for unknown reason. The only process of btsync is running on the system and the disk isn't an external storage. I recreated btsync folders on the both sides and syncronization started. But I'm in trouble what happens with .sync folder?