Firefox stores the credentials to login to the Firefox account in the Password Manager (logins.json in the Firefox profile folder). This login is hidden from about:logins. If Firefox isn't able to connect on startup then it is possible/likely that this isn't working correctly and there is a problem with logins.json or you have other software that cleans up this file. You can inspect <b>logins.json</b> to see if you see the <b>chrome://FirefoxAccounts</b> entry. You can use the button on the "Help -> More Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the <b>about:profiles</b> page (Root directory). *Help -> More Troubleshooting Information -> Profile Folder/Directory:<br>Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder *https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data