After I input the code on second device in "Pair a Device" dialog and click "Next" button I always return to "Firefox Sync Setup" dialog (without any error message) and devices stay not paired.
Thanks for quick response. I already read this troubleshooting guide.
And it not solves the problem.
The Sync works fine with Firefox 17.x but once I installing 18.0.1 version it stop to Sync devices.