sorry for my bad russian )) will try to explain... PC FF logins are empty... file logins.json.corrupt after renaming to logins.json and turning on FF again renamed in .corrupt... and one more thing... logins.json.corrupt is binary file not text... i cant understand how to restore my logins stored in androin in to desctop version!!

and i`m affraid that synch of android.. no can delete logins on them

SOLVED setup FF 56 on another PC... it synch good.. then copy files key3 and logins.json.. to my pc... all good... but stil cant understand wil my PC did not synch automaticaly!!??

Well done.

I cannot fully explain why this happened. It’s not described in the release notes for your version (of which we’re not sure whether this is 55.0, 55.0.1, 55.0.2 or 55.0.3 - you should of course use the latest - and you didn’t name the Android version either although I assume that’s trivial), but there have been reports of profile corruption with that version. Looking at this and this bug (and perhaps this and this bug) however tells us other versions may be affected too.

If you really want to find out what happened, reproduce the issue and look at the Browser Console or use about:sync-log to see if any logs match with what’s posted there. These logs may actually still exist, so you don’t even need to reproduce. One of these bugs mentions A/V software to be a possible cause too.