Every time I open Firefox, it prompts me for my Primary Password immediately. Skipping the dialog the first time opens a second, identical dialog. It's not being caused by any add-on/extension, because the problem occurs in exactly the same way in Troubleshoot Mode. It's not Sync, because I'm not signed into any Mozilla account. An internet search showed me a page here indicating I should disable Primary Password, then re-enable it. This didn't fix the problem.