I've installed EverSync extension also on Opera other than Chrome, but on Opera when I clicked on "Start Synchronization" my bookmarks on the cloud got deleted! Luckily I did previously a server backup that allowed me to restore my bookmarks, and now that I've done a manual sync selecting "Download" option and I think that the problem should be solved; it is possible that the problem was caused by the version of EverSync on the Opera AddOns Store being much older than the chrome version (version 6 vs version 19)?
Anyways kudos for this great add-on that is a life saver when working with multiple browsers on multiple devices! Regards
Customer support service by UserEcho