If the Saved Passwords option is selected for Custom history, I am unable to directly Sync with my current account. It appears as if I never set up Sync. Found this while toying with the Custom History setting in FF preferences. As a result, though, I had to enter my Sync account manually to "restore it" for use on my Mac FF install and on my previously activated devices. Preferences > Privacy > History Select: Firefox will: "Use custom setting for history" Select: Clear history when Firefox closes Select: the Settings button Under Data, check the Saved Passwords box. Close FireFox Restart FireFox You will notice that instead of the usual "Sync Now" option under Tools, you are back to "Set Up Sync..." This might fool the user into thinking the account is gone, but it is not. Unfortunately, it does appear that the active devices are gone. Current workaround to get back in: Tools > Set Up Sync > Connect Select the "I don't have the device with me link" Type in the Account, password, etc. Current workaround to prevent this from happening: Custom History settings are OK, just do not check the Saved Passwords boxes to avoid clearing the Password information.
Got it, thanks for finding that older bug.