Please do not create duplicate threads, you have already posted this: https://support.mozilla.org/en-US/questions/1013454

making duplicate posts will not fix your issues any quicker then if you just have the one post and can infact cause confusion for others and waste time answering the question that may have already been answered

TechBoss,

Thanks for reporting this! :) I'm locking this thread as a duplicate.

Xendler Please do not create duplicate threads. Please read the Mozilla Support rules and guidelines

EDIT: Actually, it looks like cor-el has already locked the other one and pointed back here. No need to lock this. Please wait for a contributor to assist you soon. I guess the "reported posts" needed to be cleared.

in the case of the answers will be? I do not care about the second thread, created due to a bug with registration

Ok this is a bug acutally that the engineers are working on this past week. There were some 502 an 503 errors that this unknown error message is detecting.

Bug is 1045691 - Firefox sync fails with "unknown error" graybar message and 502s

For updates please refer to the bug, the eta for the fix is ymmv this week.