Hi cobranic, Please make sure that both computers are connected to the correct Firefox Sync server. If you try to login at accounts.firefox.com and click on "Already have an account" on the new computer does the account login?

Make sure that you allow cookies for the accounts.firefox.com domain if you aren't allowing cookies generally or use the 'Ask me' cookie setting or use extensions that deal with cookies. Try to delete the Weave folder and the signedInUser.json file in the Firefox profile folder and delete the prefs.js files to reset all prefs and maybe also delete the compatibility.ini file to reinitialize the profile. You can use this button to go to the currently used Firefox profile folder: *Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder) *http://kb.mozillazine.org/Profile_folder_-_Firefox ---- Create a new profile as a test to check if your current profile is causing the problem. See "Creating a profile": *https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles *http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems. *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox