Is this about connecting to Sync or about another website ?
Can you login to the Firefox Account via this web page?
You can try these steps in case of issues with webpages:
You can reload webpage(s) and bypass the cache to refresh possibly outdated or corrupted files.
- hold down the Shift key and left-click the Reload button
- press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
- press "Command + Shift + R" (Mac)
Clear the Cache and remove the Cookies for websites that cause problems via the "3-bar" Firefox menu button (Settings).
"Remove the Cookies" for websites that cause problems:
- Settings -> Privacy & Security
Cookies and Site Data: "Manage Data"
"Clear the Cache":
- Settings -> Privacy & Security
Cookies and Site Data -> Clear Data -> [X] Cached Web Content -> Clear
Start Firefox in Troubleshoot Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration or if userChrome.css/userContent.css is causing the problem.
- switch to the Default System theme: "3-bar" menu button or Tools -> Add-ons -> Themes
- do NOT click the "Refresh Firefox" button on the Troubleshoot Mode start window
Is this about connecting to Sync or about another website ?
Can you login to the Firefox Account via this web page?
*https://accounts.firefox.com/signin
*https://accounts.firefox.com/settings
You can try these steps in case of issues with webpages:
You can reload webpage(s) and bypass the cache to refresh possibly outdated or corrupted files.
*hold down the Shift key and left-click the Reload button
*press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
*press "Command + Shift + R" (Mac)
Clear the Cache and remove the Cookies for websites that cause problems via the "3-bar" Firefox menu button (Settings).
"Remove the Cookies" for websites that cause problems:
*Settings -> Privacy & Security<br>Cookies and Site Data: "Manage Data"
"Clear the Cache":
*Settings -> Privacy & Security<br>Cookies and Site Data -> Clear Data -> [X] Cached Web Content -> Clear
*https://support.mozilla.org/en-US/kb/clear-cookies-and-site-data-firefox
*https://support.mozilla.org/en-US/kb/how-clear-firefox-cache
Start Firefox in <b>Troubleshoot Mode</b> to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if <b>hardware acceleration</b> or if <b>userChrome.css/userContent.css</b> is causing the problem.
*switch to the Default System theme: "3-bar" menu button or Tools -> Add-ons -> Themes
*do NOT click the "Refresh Firefox" button on the Troubleshoot Mode start window
*https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
*https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems
*https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop
*https://support.mozilla.org/en-US/kb/smartblock-enhanced-tracking-protection
*https://support.mozilla.org/en-US/kb/trackers-and-scripts-firefox-blocks-enhanced-track