Hello, I have 3 - 64bit Windows 10 (Creators version) computers, a desktop, a Surface and this one, a laptop. All have Firefox 56 (64 bit) installed. All are on a common sync account. I am trying to sync Bookmarks only. I have successfully synced test Bookmarks in both directions between the desktop and Surface and from the sync account to the laptop. The laptop is the primary Bookmarks repository and receives sync errors every time it attempts to upload to the sync account. I have done a fresh install of Firefox 56 on the laptop and run SQLite Forensic Explorer on places.sqlite which showed no errors, still no success in uploading Bookmarks from the laptop to the sync account. I have attached the laptop sync log file for reference. Hope you can make determine the issue. Please contact me if you need further info.